发信人:&Roland&(楼兰),&信区:&Java&&&&&&&
标&&题:&Re:&Enterprise&JavaBeans&和&JavaBean的比较
发信站:&BBS&水木清华站&(Wed&May&&3&19:49:26&2000)
【&在&liyawei&(lili)&的大作中提到:&】
:&我想,EJB绝对是和COM竞争的.
:&微软为什么要力推DNA架构,就是想在
:&服务端使用分布式的COM+对象.其
:&WINDOWS2000中的COM+服务已经包括了
:&分布式事务\安全等各种服务器端必须的服务.
:&而EJB是通过其CONTAINER来享受整个J2EE提供的服务.
:&目前的JAVA应用服务器中,也只是
:&尽量能支持COM与EJB对象通信,而罕见在服务一级上
:&对COM提供借口.在客户端对COM的支持需要MS自己的JAVA&
:&另外,既然前端我用惯了MS的一套东西,
:&用惯了ASP\COM\windows,我为什么还要在服务端选择
:&EJB(因为我不懂也不想懂JAVA),而不是使用和微软一套
:&更和谐的COM+呢?
我觉得在服务器端，window2000是不可能一统天下的&，另外，ejb实际上是扩展了
CORBA，而且得到了OMG（也就是700家公司）的支持。在国外，开发enterprise
application&一般是EJB+JSP/Servlet+JDBC,(from&a&article&on&Javaworld).
我觉得，java会更有前途的
※&来源:·BBS&水木清华站&smth.org·[FROM:&162.105.38.74]
发信人:&Roland&(楼兰),&信区:&Java&&&&&&&
标&&题:&java&certificate&example
发信站:&BBS&水木清华站&(Sat&Apr&15&10:37:51&2000)
Certificates
To&verify&a&signature,&you&need&the&signer's&public&key.&So&how&are&public&k
eys&distributed&securely?&You&could&simply&download&the&key&from&a&server&so
mewhere,&but&how&would&you&know&you&got&the&right&file&and&not&a&forgery?&Ev
en&if&you&get&a&valid&key,&how&do&you&know&that&it&belongs&to&a&particular&p
Certificates&answer&these&questions.&A&certificate&is&a&statement,&signed&by
&one&person,&that&the&public&key&of&another&person&has&a&particular&value.&I
n&some&ways,&it's&like&a&driver's&license.&The&license&is&a&document&issued&
by&your&state&government&that&matches&your&face&to&your&name,&address,&and&d
ate&of&birth.&When&you&buy&alcohol,&tobacco,&or&dirty&magazines,&you&can&use
&your&license&to&prove&your&identity&(and&your&age).
Note&that&the&license&only&has&value&because&you&and&your&local&shopkeepers&
trust&the&authority&of&the&state&government.&Digital&certificates&have&the&s
ame&property:&You&need&to&trust&the&person&who&issued&the&certificate&(who&i
s&known&as&a&Certificate&Authority,&or&CA).
In&cryptographic&terminology,&a&certificate&associates&an&identity&with&a&pu
blic&key.&The&identity&is&called&the&subject.&The&identity&that&signs&the&ce
rtificate&is&the&signer.&The&certificate&contains&information&about&the&subj
ect&and&the&subject's&public&key,&plus&information&about&the&signer.&The&who
le&thing&is&cryptographically&signed,&and&the&signature&becomes&part&of&the&
certificate,&too.&Because&the&certificate&is&signed,&it&can&be&freely&distri
buted&over&insecure&channels.
At&a&basic&level,&a&certificate&contains&these&elements:
Information&about&the&subject
The&subject's&public&key
Information&about&the&issuer
The&issuer's&signature&of&the&above&information
Sun&recognized&that&certificate&support&was&anemic&in&JDK&1.1.&Things&are&im
proved&in&JDK&1.2.&You&can&now&import&X.509v3&certificates&and&verify&them.&
You&still&can't&generate&a&certificate&using&the&public&API.
In&this&section,&I'll&talk&about&the&JDK&1.2&classes&that&represent&certific
ates&and&Certificate&Revocation&Lists&(CRLs).
java.security.cert.Certificate
JDK&1.1&introduced&support&for&certificates,&based&around&the&java.security.
Certificate&interface.&In&JDK&1.2,&this&interface&is&&we&won't&be
&covering&it.&It&is&replaced&by&an&abstract&class,&java.security.cert.Certif
icate.&This&class&is&a&little&simpler&than&its&predecessor,&and&it&includes&
the&ability&to&verify&a&certificate.&Support&for&X.509&certificates&is&provi
ded&in&a&separate&class,&which&I'll&explain&in&a&moment.
First,&of&course,&java.security.cert.Certificate&is&a&container&for&a&public
public&abstract&PublicKey&getPublicKey()
This&method&returns&the&public&key&that&is&contained&by&this&certificate.
You&can&get&an&encoded&version&of&the&certificate&using&getEncoded().&The&da
ta&returned&by&this&method&could&be&written&to&a&file:
public&abstract&byte[]&getEncoded()&throws&CertificateEncodingException
This&method&returns&an&encoded&representation&of&the&certificate.
Generating&a&Certificate
Oddly&enough,&there&is&still&no&programmatic&way&to&generate&a&certificate&f
rom&scratch,&even&with&the&new&classes&in&JDK&1.2.&You&can,&however,&load&an
&X.509&certificate&from&a&file&using&the&getInstance()&method&in&the&X509Cer
tificate&class.&I'll&talk&about&this&later.
Working&with&certificates&in&JDK&1.2&is&sometimes&difficult&because&there&ar
e&two&things&named&Certificate.&The&java.security.Certificate&interface&was&
introduced&in&JDK&1.1,&but&it's&now&deprecated.&The&"official"&certificate&c
lass&in&JDK&1.2&is&java.security.cert.Certificate.&Whenever&you&see&Certific
ate&in&source&code,&make&sure&you&understand&what&it&refers&to.&And&be&caref
ul&if&you&import&both&java.security.*&and&java.security.cert.*.
Verifying&a&Certificate
To&verify&the&contents&of&the&certificate,&use&one&of&the&verify()&methods:
public&abstract&void&verify(PublicKey&key)&throws&CertificateException,&NoSu
chAlgorithmException,&InvalidKeyException,&NoSuchProviderException,&Signatur
eException
This&method&uses&the&supplied&public&key&to&verify&the&certificate's&content
s.&The&public&key&should&belong&to&the&certificate's&issuer&(and&has&nothing
&to&do&with&the&public&key&contained&in&this&certificate).&The&supplied&issu
er's&public&key&is&used&to&verify&the&internal&signature&that&protects&the&i
ntegrity&of&the&certificate's&data.
public&abstract&void&verify(PublicKey&key,&String&sigProvider)&throws&Certif
icateException,&NoSuchAlgorithmException,&InvalidKeyException,&NoSuchProvide
rException,&SignatureException
This&is&the&same&as&the&previous&method,&but&specifically&uses&the&given&pro
vider&to&supply&the&signing&algorithm&implementation.
Several&standards&specify&the&contents&of&a&certificate.&One&of&the&most&pop
ular&is&X.509,&published&by&the&International&Telecommunications&Union&(ITU)
.&Three&versions&of&this&standard&have&been&published.&Table&6-1&shows&the&c
ontents&of&an&X.509&certificate.
Support&for&X.509&certificates&is&provided&by&a&subclass&of&Certificate,&jav
a.security.cert.X509Certificate.&This&class&is&also&abstract&although&it&def
ines&a&getInstance()&method&that&returns&a&concrete&subclass.&Most&of&the&me
thods&in&this&class&return&the&fields&of&an&X.509&certificate:&getVersion(),
&getSerialNumber(),&getIssuerDN(),&and&so&on.&Table&6-1&shows&the&X509Certif
icate&methods&corresponding&to&the&certificate&fields.
Table&6-1:&X.509&Certificate&Contents&&Field
&Description
&X.509&v1,&v2,&or&v3
&int&getVersion()
Serial&number
&A&number&unique&to&the&issuer
&BigInteger&getSerialNumber()
Signature&algorithm
&Describes&the&cryptographic&algorithm&used&for&the&signature
&String&getSigAlgName()
&The&issuer's&name
&Principal&getIssuerDN()
Validity&period
&A&range&of&time&when&the&certificate&is&valid
&Date&getNotBefore(),&Date&getNotAfter()
&The&subject's&name
&Principal&getSubjectDN()
Subject's&public&key
&The&subject's&public&key
&PublicKey&getPublicKey()&(inherited&from&Certificate)
Issuer's&unique&identifier
&A&unique&identifier&representing&the&issuer&(versions&2&and&3)
&boolean[]&getIssuerUniqueID()
Subject's&unique&identifier
&A&unique&identifier&representing&the&subject&(versions&2&and&3)
&boolean[]&getSubjectUniqueID()
Extensions
&Additional&data&(version&3)
&boolean[]&getKeyUsage(),&int&getBasicConstraints()
&A&signature&of&all&of&the&previous&fields
&byte[]&getSignature()
To&load&an&X.509&certificate&from&a&file,&you&can&use&getInstance():
public&static&final&X509Certificate&getInstance(InputStream&inStream)&throws
&CertificateException
This&method&instantiates&a&concrete&subclass&of&X509Certificate&and&initiali
zes&it&with&the&given&input&stream.
public&static&final&X509Certificate&getInstance(byte[]&certData)&throws&Cert
ificateException
This&method&works&as&above,&except&the&new&certificate&is&initialized&using&
the&supplied&byte&array.
The&way&that&getInstance()&works&is&a&little&convoluted.&The&actual&object&t
hat&is&created&is&determined&by&an&entry&in&the&java.security&properties&fil
e.&This&file&is&found&in&the&lib/security&directory&underneath&the&JDK&insta
llation&directory.&By&default,&the&relevant&line&looks&like&this:
cert.provider.x509=sun.security.x509.X509CertImpl
Let's&say&you&call&getInstance()&with&an&input&stream.&A&sun.security&.x509.
X509CertImpl&will&be&created,&using&a&constructor&that&accepts&the&input&str
eam.&It's&up&to&the&X509CertImpl&to&read&data&from&the&input&stream&to&initi
alize&itself.&X509CertImpl&knows&how&to&construct&itself&from&a&DER-encoded&
certificate.&What&is&DER?&In&the&X.509&standard,&a&certificate&is&specified&
as&a&data&structure&using&the&ASN.1&(Abstract&Syntax&Notation)&language.&The
re&are&a&few&different&ways&that&ASN.1&data&structures&can&be&reduced&to&a&b
yte&stream,&and&DER&(Distinguished&Encoding&Rules)&is&one&of&these&methods.&
The&net&result&is&that&an&X509CertImpl&can&recognize&an&X.509&certificate&if
&it&is&DER-encoded.
Let's&look&at&an&example&that&uses&X509Certificate.&We'll&write&a&tool&that&
displays&information&about&a&certificate&contained&in&a&file,&just&like&keyt
ool&-printcert.&Like&keytool,&we'll&recognize&certificate&files&in&the&forma
t&described&by&RFC&1421.&An&RFC&1421&certificate&representation&is&simply&a&
DER&representation,&converted&to&base64,&with&a&header&and&a&footer&line.&He
re&is&such&a&file:
-----BEGIN&CERTIFICATE-----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-----END&CERTIFICATE-----
Our&class&performs&three&tasks:
We&need&to&read&the&file,&strip&off&the&header&and&footer,&and&convert&the&b
ody&from&a&base64&string&to&a&byte&array.&The&oreilly.jonathan.util.Base64&c
lass&is&used&to&perform&the&base64&conversion.&This&class&is&presented&in&Ap
pendix&B,&Base64.
We'll&use&this&byte&array&(a&DER-encoded&certificate)&to&create&a&new&X509Ce
rtificate.&We&can&then&print&out&some&basic&information&about&the&certificat
Finally,&we'll&calculate&certificate&fingerprints&and&print&them.
Spill&begins&by&checking&its&command-line&arguments:
import&java.io.*;
import&java.security.KeyS
import&java.security.MessageD
import&java.security.cert.X509C
import&oreilly.jonathan.util.Base64;
public&class&Spill&{
&&public&static&void&main(String[]&args)&throws&Exception&{
&&&&if&(args.length&!=&1)&{
&&&&&&System.out.println("Usage:&Spill&file");
Next,&Spill&creates&a&BufferedReader&for&reading&lines&of&text&from&the&file
.&If&the&first&line&doesn't&contain&the&certificate&header,&an&exception&is&
thrown.&Otherwise,&subsequent&lines&are&read&and&accumulated&as&one&large&ba
se64&string.&We&stop&reading&lines&when&we&encounter&the&footer&line.&This&d
one,&we&convert&the&base64&string&to&a&byte&array:
&&&&BufferedReader&in&=&new&BufferedReader(new&FileReader(args[0]));
&&&&String&begin&=&in.readLine();
&&&&if&(begin.equals("-----BEGIN&CERTIFICATE-----")&==&false)
&&&&&&throw&new&IOException("Couldn't&find&certificate&beginning");
&&&&String&base64&=&new&String();
&&&&boolean&trucking&=&
&&&&while&(trucking)&{
&&&&&&String&line&=&in.readLine();
&&&&&&if&(line.startsWith("-----"))&trucking&=&
&&&&&&else&base64&+=&
&&&&in.close();
&&&&byte[]&certificateData&=&Base64.decode(base64);
We&now&have&the&raw&certificate&data&and&can&create&a&new&certificate&using&
getInstance()&in&the&X509Certificate&class:
&&&&X509Certificate&c&=&X509Certificate.getInstance(certificateData);
Having&obtained&an&X509Certificate,&Spill&prints&out&various&bits&of&informa
tion&about&it.
&&&&System.out.println("Subject:&"&+&c.getSubjectDN().getName());
&&&&System.out.println("Issuer&:&"&+&c.getIssuerDN().getName());
&&&&System.out.println("Serial&number:&"&+
&&&&&&&&c.getSerialNumber().toString(16));
&&&&System.out.println("Valid&from&"&+&c.getNotBefore()&+
&&&&&&&&"&to&"&+&c.getNotAfter());
We&also&want&to&print&out&the&certificate's&fingerprints.&It's&a&little&tric
ky&to&format&the&fingerprints&correctly,&so&a&helper&method,&doFingerprint()
,&is&used:
&&&&System.out.println("Fingerprints:");
&&&&doFingerprint(certificateData,&"MD5");
&&&&doFingerprint(certificateData,&"SHA");
The&doFingerprint()&method&calculates&a&fingerprint&(message&digest&value)&a
nd&prints&it&out.&First,&it&obtains&a&message&digest&for&the&requested&algor
ithm&and&calculates&the&digest&value:
protected&static&void&doFingerprint(byte[]&certificateBytes,
&&&&&&String&algorithm)&throws&Exception&{
&&&&System.out.print("&&"&+&algorithm&+&":&");
&&&&MessageDigest&md&=&MessageDigest.getInstance(algorithm);
&&&&md.update(certificateBytes);
&&&&byte[]&digest&=&md.digest();
Now&doFingerprint()&will&print&out&the&digest&value&as&a&series&of&two-digit
&hexadecimal&numbers.&We&loop&through&the&digest&value.&Each&byte&is&convert
ed&to&a&two-digit&hex&string.&Colons&separate&the&hex&values.
&&&&for&(int&i&=&0;&i&&&digest.&i++)&{
&&&&&&if&(i&!=&0)&System.out.print(":");
&&&&&&int&b&=&digest[i]&&&0
&&&&&&String&hex&=&Integer.toHexString(b);
&&&&&&if&(hex.length()&==&1)&System.out.print("0");
&&&&&&System.out.print(hex);
&&&&System.out.println();
Let's&take&it&for&a&test&drive.&Let's&say&you&have&a&certificate&in&a&file&n
amed&ca1.x509.&You&would&run&Spill&as&follows:
C:\&java&Spill&ca1.x509
Subject:&T="+42&38&",&OID.1.2.840..9.1=,&CN=
Libor&Dostalek,&OU=VCU,&O="PVT,a.s.",&L=Ceske&Budejovice,&S=2,&C=CZ
Issuer&:&OID.1.2.840..9.1=ca-oper@p70x03.brn.pvt.cz,&CN=CA-PVT1,&O=P
VT&a.s.,&C=CZ
Serial&number:&2d
Valid&from&Mon&Aug&04&01:04:56&EDT&1997&to&Tue&Feb&03&00:04:56&EST&1998
Fingerprints:
&&MD5:&d9:6f:56:3e:e0:ec:35:70:94:bb:df:05:75:d6:32:0e
&&SHA:&db:be:df:e5:ff:ec:f9:53:98:dc:88:dd:6b:ba:cf:2e:2a:68:0c:44
If&you&run&keytool&-printcert&on&the&same&file,&you'll&see&the&same&informat
C:\&keytool&-printcert&-file&ca1.x509
Owner:&T="+42&38&",&OID.1.2.840..9.1=,&CN=Li
bor&Dostalek,&OU=VCU,&O="PVT,a.s.",&L=Ceske&Budejovice,&S=2,&C=CZ
Issuer:&OID.1.2.840..9.1=ca-oper@p70x03.brn.pvt.cz,&CN=CA-PVT1,&O=PV
T&a.s.,&C=CZ
Serial&Number:&2d
Valid&from:&Mon&Aug&04&01:04:56&EDT&1997&until:&Tue&Feb&03&00:04:56&EST&1998
Certificate&Fingerprints:
&&&&&&&&&MD5:&&D9:6F:56:3E:E0:EC:35:70:94:BB:DF:05:75:D6:32:0E
&&&&&&&&&SHA1:&DB:BE:DF:E5:FF:EC:F9:53:98:DC:88:DD:6B:BA:CF:2E:2A:68:0C:44
Certificate&Revocation&Lists
JDK&1.2&addresses&another&shortcoming&of&the&JDK&1.1&certificate&support:&Ce
rtificate&Revocation&Lists&(CRLs).&CRLs&answer&the&question&of&what&happens&
to&certificates&when&they're&lost&or&stolen.&A&CRL&is&simply&a&list&of&certi
ficates&that&are&no&longer&valid.&(Unfortunately,&there&aren't&yet&any&stand
arts&for&how&CRLs&are&&presumably&they're&published&in&some&way&by&th
e&CAs.)&JDK&1.2&provides&two&classes&that&support&CRLs.&First,&java.security
.cert.X509CRL&represents&a&CRL&as&specified&in&the&X.509&standard.&You&can&c
reate&an&X509CRL&from&a&file&using&getInstance(),&just&as&with&X509Certifica
public&static&final&X509CRL&getInstance(InputStream&inStream)&throws&CRLExce
ption,&X509ExtensionException
This&method&instantiates&a&concrete&subclass&of&X509CRL&and&initializes&it&w
ith&the&given&input&stream.
public&static&final&X509CRL&getInstance(byte[]&crlData)&throws&CRLException,
&X509ExtensionException
This&method&works&like&the&preceding&method&except&it&uses&the&supplied&byte
&array&to&initialize&the&X509CRL.
X509CRL's&getInstance()&works&in&much&the&same&way&as&X509Certificate.&The&a
ctual&subclass&of&X509CRL&that&is&returned&by&getInstance()&is&determined,&a
gain,&by&an&entry&in&the&java.security&file.&The&relevant&entry&for&CRLs&is&
crl.provider.x509=sun.security.x509.X509CRLImpl
X509CRL&is&similar&to&X509Certificate&in&many&ways.&It&includes&getEncoded()
&and&verify()&methods&that&accomplish&the&same&thing&as&in&X509Certificate.&
It&also&includes&methods&that&return&information&about&the&CRL&itself,&like&
getIssuerDN()&and&getSigAlgName().
To&find&out&if&a&particular&certificate&has&been&revoked,&you&can&use&the&is
Revoked()&method:
public&abstract&boolean&isRevoked(BigInteger&serialNumber)
This&method&returns&true&if&the&certificate&matching&the&given&serial&number
&has&been&revoked.&Serial&numbers&are&unique&to&a&Certificate&Authority&(CA)
.&Each&CA&issues&its&own&CRLs.&Thus,&this&method&is&used&to&correlate&certif
icate&serial&numbers&from&the&same&CA.
If&you&want&more&information&about&a&revoked&certificate,&you&can&use&the&ge
tRevokedCertificate()&and&getRevokedCertificates()&methods.&These&return&ins
tances&of&java.security.cert.RevokedCertificate,&which&can&be&used&to&check&
the&revocation&date:
public&abstract&RevokedCertificate&getRevokedCertificate(BigInteger&serialNu
mber)&throws&CRLException
This&method&returns&a&RevokedCertificate&corresponding&to&the&given&serial&n
public&abstract&Set&getRevokedCertificates()&throws&CRLException
This&method&returns&a&collection&of&all&the&revoked&certificates&contained&i
n&this&X509CRL.
----------------------------------------------------------------------------
1.&These&methods&are&based&on&the&authentication&procedures&outlined&in&the&
X.509&standard,&published&by&the&International&Telecommunications&Union&(ITU
).&Although&X.509&is&best&known&for&its&certificate&definition,&the&document
&concerns&the&general&problem&of&authentication.&For&more&information,&you&c
an&download&the&document&from&the&ITU&at&http://www.itu.ch/.
2.&In&practice,&it&just&takes&a&very,&very&long&time&to&figure&out&what&inpu
t&produced&a&given&digest&value.
※&来源:·BBS&水木清华站&smth.org·[FROM:&162.105.18.201]
发信人:&Roland&(楼兰),&信区:&Java&&&&&&&
标&&题:&java&Signature&example
发信站:&BBS&水木清华站&(Sat&Apr&15&10:36:06&2000)
Signatures
A&signature&provides&two&security&services,&authentication&and&integrity.&A&
signature&gives&you&assurance&that&a&message&has&not&been&tampered&with&and&
that&it&originated&from&a&certain&person.&As&you'll&recall&from&Chapter&2,&a
&signature&is&a&message&digest&that&is&encrypted&with&the&signer's&private&k
ey.&Only&the&signer's&public&key&can&decrypt&the&signature,&which&provides&a
uthentication.&If&the&message&digest&of&the&message&matches&the&decrypted&me
ssage&digest&from&the&signature,&then&integrity&is&also&assured.
Signatures&do&not&provide&confidentiality.&A&signature&accompanies&a&plainte
xt&message.&Anyone&can&intercept&and&read&the&message.&Signatures&are&useful
&for&distributing&software&and&documentation&because&they&foil&forgery.
The&Java&Security&API&provides&a&class,&java.security.Signature,&that&repres
ents&cryptographic&signatures.&This&class&operates&in&two&distinct&modes,&de
pending&on&whether&you&wish&to&generate&a&signature&or&verify&a&signature.
Like&the&other&cryptography&classes,&Signature&has&two&factory&methods:
public&static&Signature&getInstance(String&algorithm)&throws&NoSuchAlgorithm
This&method&returns&a&Signature&for&the&given&algorithm.&The&first&provider&
supporting&the&given&algorithm&is&used.
public&static&Signature&getInstance(String&algorithm,&String&provider)&throw
s&NoSuchAlgorithmException,&NoSuchProviderException
This&method&returns&a&Signature&for&the&given&algorithm,&using&the&given&pro
One&of&two&methods&initializes&the&Signature:
public&final&void&initSign(PrivateKey&privateKey)&throws&InvalidKeyException
If&you&want&to&generate&a&signature,&use&this&method&to&initialize&the&Signa
ture&with&the&given&private&key.
public&final&void&initVerify(PublicKey&publicKey)&throws&InvalidKeyException
To&verify&a&signature,&call&this&method&with&the&public&key&that&matches&the
&private&key&that&was&used&to&generate&the&signature.
If&you&want&to&set&algorithm-specific&parameters&in&the&Signature&object,&yo
u&can&pass&an&AlgorithmParameterSpec&to&setParameter().
public&final&void&setParameter(AlgorithmParameterSpec&params)&throws&Invalid
AlgorithmPararmeterException
You&can&pass&algorithm-specific&parameters&to&a&Signature&using&this&object.
&If&the&Signature&does&not&recognize&the&AlgorithmParameterSpec&object,&an&e
xception&is&thrown.
You&can&add&data&to&a&Signature&the&same&way&as&for&a&message&digest,&using&
the&update()&methods.&A&SignatureException&is&thrown&if&the&Signature&has&no
t&been&initialized.
public&final&void&update(byte&input)&throws&SignatureException
You&can&add&a&single&byte&to&the&Signature's&input&data&using&this&method.
public&final&void&update(byte[]&input)&throws&SignatureException
This&method&adds&the&given&array&of&bytes&to&the&Signature's&input&data.
public&final&void&update(byte[]&input,&int&offset,&int&len)&throws&Signature
This&method&adds&len&bytes&from&the&given&array,&starting&at&offset,&to&the&
Signature's&input&data.
Generating&a&Signature
Generating&a&signature&is&a&lot&like&generating&a&message&digest&value.&The&
sign()&method&returns&the&signature&itself:
public&final&byte[]&sign()&throws&SignatureException
This&method&calculates&a&signature,&based&on&the&input&data&as&supplied&in&c
alls&to&update().&A&SignatureException&is&thrown&if&the&Signature&is&not&pro
perly&initialized.
To&generate&a&signature,&you&will&need&the&signer's&private&key&and&the&mess
age&that&you&wish&to&sign.&The&procedure&is&straightforward:
Obtain&a&Signature&object&using&the&getInstance()&factory&method.&You'll&nee
d&to&specify&an&algorithm.&A&signature&actually&uses&two&algorithms--one&to&
calculate&a&message&digest&and&one&to&encrypt&the&message&digest.&The&SUN&pr
ovider&shipped&with&the&JDK&1.1&supports&DSA&encryption&of&an&SHA-1&message&
digest.&This&is&simply&referred&to&as&DSA.
Initialize&the&Signature&with&the&signer's&private&key&using&initSign().
Use&the&update()&method&to&add&the&data&of&the&message&into&the&signature.&Y
ou&can&call&update()&as&many&times&as&you&would&like.&Three&different&overlo
ads&allow&you&to&update&the&signature&with&byte&data.
Calculate&the&signature&using&the&sign()&method.&This&method&returns&an&arra
y&of&bytes&that&are&the&signature&itself.&It's&up&to&you&to&store&the&signat
ure&somewhere.
Verifying&a&Signature
You&can&use&Signature's&verify()&method&to&verify&a&signature:
public&final&boolean&verify(byte[]&signature)&throws&SignatureException
This&method&verifies&that&the&supplied&byte&array,&signature,&matches&the&in
put&data&that&has&been&supplied&using&update().&If&the&signature&verifies,&t
rue&is&returned.&If&the&Signature&is&not&properly&initialized,&a&SignatureEx
ception&is&thrown.
Verifying&a&signature&is&similar&to&generating&a&signature.&In&fact,&Steps&1
&and&3&are&identical.&It's&assumed&that&you&already&have&a&signature&value.&
The&process&here&verifies&that&the&message&you've&received&produces&the&same
&signature:
Obtain&a&Signature&using&the&getInstance()&factory&method.
Initialize&the&Signature&with&the&signer's&public&key&using&initVerify().
Use&update()&to&add&message&data&into&the&signature.
Check&if&your&signatures&match&using&the&verify()&method.&This&method&accept
s&an&array&of&bytes&that&are&the&signature&to&be&verified.&It&returns&a&bool
ean&value&that&is&true&if&the&signatures&match&and&false&otherwise.
Let's&examine&a&complete&program,&called&Hancock,&that&generates&and&verifie
s&signatures.&We'll&use&a&file&for&the&message&input,&and&we'll&pull&keys&ou
t&of&a&KeyStore.&(You&can&manipulate&keystores&with&the&keytool&utility,&des
cribed&in&Chapter&5,&Key&Management.&To&run&this&example,&you'll&have&to&hav
e&created&a&keystore&with&at&least&one&key&pair.)&Hancock&is&a&command-line&
utility&that&accepts&parameters&as&follows:
java&Hancock&-s|-v&keystore&storepass&alias&messagefile&signaturefile
The&-s&option&is&used&for&signing.&The&private&key&of&the&given&alias&is&use
d&to&create&a&signature&from&the&data&contained&in&messagefile.&The&resultin
g&signature&is&stored&in&signaturefile.&The&keystore&parameter&is&the&filena
me&of&a&keystore,&and&storepass&is&the&password&needed&to&access&the&keystor
The&-v&option&tells&Hancock&to&verify&a&signature.&The&signature&is&assumed&
to&be&in&signaturefile.&Hancock&verifies&that&the&signature&is&from&the&give
n&alias&for&the&data&contained&in&messagefile.&Again,&keystore&is&a&keystore
&file,&and&storepass&is&used&to&access&the&keystore.
Let's&begin&by&checking&our&command-line&arguments:
import&java.io.*;
import&java.security.*;
public&class&Hancock&{
&&public&static&void&main(String[]&args)&throws&Exception&{
&&&&if&(args.length&!=&6)&{
&&&&&&System.out.println(
&&&&&&&&&&"Usage:&Hancock&-s|-v&keystore&storepass&alias&"&+
&&&&&&&&&&"messagefile&signaturefile");
&&&&String&options&=&args[0];
&&&&String&keystorefile&=&args[1];
&&&&String&storepass&=&args[2];
&&&&String&alias&=&args[3];
&&&&String&messagefile&=&args[4];
&&&&String&signaturefile&=&args[5];
Our&first&step,&as&you'll&recall,&is&the&same&for&signing&and&verifying:&We&
need&to&get&a&Signature&object.&We&use&DSA&because&it's&supplied&with&the&Su
n&provider:
&&&&Signature&signature&=&Signature.getInstance("DSA");
Next,&the&Signature&needs&to&be&initialized&with&either&the&public&key&or&th
e&private&key&of&the&named&alias.&In&either&case,&we&need&a&reference&to&the
&keystore,&which&we&obtain&as&follows:
&&&&KeyStore&keystore&=&KeyStore.getInstance();
&&&&keystore.load(new&FileInputStream(keystorefile),&storepass);
To&sign,&we&initialize&the&Signature&with&a&private&key.&The&password&for&th
e&private&key&is&assumed&to&be&the&same&as&the&keystore&password.&To&verify,
&we&initialize&the&Signature&with&a&public&key.
&&&&if&(options.indexOf("s")&!=&-1)
&&&&&&signature.initSign(keystore.getPrivateKey(alias,&storepass));
&&&&&&signature.initVerify(keystore.getCertificate(alias).getPublicKey());
The&next&step&is&to&update&the&signature&with&the&given&message.&This&step&i
s&the&same&whether&we&are&signing&or&verifying.&We&open&the&message&file&and
&read&it&in&8K&chunks.&The&signature&is&updated&with&every&byte&read&from&th
e&message&file.
&&&&FileInputStream&in&=&new&FileInputStream(messagefile);
&&&&byte[]&buffer&=&new&byte[8192];
&&&&while&((length&=&in.read(buffer))&!=&-1)
&&&&&&signature.update(buffer,&0,&length);
&&&&in.close();
Finally,&we're&ready&to&sign&the&message&or&verify&a&signature.&If&we're&sig
ning,&we&simply&generate&a&signature&and&store&it&in&a&file.
&&&&if&(options.indexOf("s")&!=&-1)&{
&&&&&&FileOutputStream&out&=&new&FileOutputStream(signaturefile);
&&&&&&byte[]&raw&=&signature.sign();
&&&&&&out.write(raw);
&&&&&&out.close();
Otherwise,&we&are&verifying&a&signature.&All&we&need&to&do&is&read&in&the&si
gnature&and&check&if&it&verifies.&We'll&print&out&a&message&to&the&user&that
&tells&if&the&signature&verified.
&&&&else&{
&&&&&&FileInputStream&sigIn&=&new&FileInputStream(signaturefile);
&&&&&&byte[]&raw&=&new&byte[sigIn.available()];
&&&&&&sigIn.read(raw);
&&&&&&sigIn.close();
&&&&&&if&(signature.verify(raw))
&&&&&&&&System.out.println("The&signature&is&good.");
&&&&&&else
&&&&&&&&System.out.println("The&signature&is&bad.");
You&can&use&Hancock&to&sign&any&file&with&any&private&key&that's&in&a&keysto
re.&A&friend&who&has&your&public&key&can&use&Hancock&to&verify&a&file&he&or&
she&has&downloaded&from&you.
Login,&Again
Passwords&are&a&simple&solution&to&authentication,&but&they&are&not&consider
ed&very&secure.&People&choose&easy-to-guess&passwords,&or&they&write&down&pa
sswords&in&obvious&places.&A&sly&malcontent,&pretending&to&be&a&system&admin
istrator,&can&usually&convince&a&user&to&tell&his&or&her&password.
If&you&want&a&stronger&form&of&authentication,&and&you&are&willing&to&pay&th
e&price&in&complexity,&then&you&should&use&a&signature-based&authentication&
The&basic&procedure&is&very&similar&to&the&password-based&schemes&examined&e
arlier,&in&the&section&on&message&digests.&The&client&generates&a&timestamp&
and&a&random&number.&This&time,&the&client&creates&a&signature&of&this&data&
and&sends&it&to&the&server.&The&server&can&verify&the&signature&with&the&cli
ent's&public&key.
How&does&the&client&access&your&private&key,&to&generate&a&signature?&In&a&r
eal&application,&you&would&probably&point&the&client&to&a&disk&file&that&con
tained&your&key&(preferably&on&removable&media,&like&a&floppy&disk&or&a&smar
t&card).&In&this&example,&we'll&just&pull&a&private&key&out&of&a&keystore.
The&hard&part&is&in&creating&and&maintaining&the&public&key&database.&The&se
rver&needs&to&have&a&public&key&for&every&possible&person&who&will&log&in.&F
urthermore,&the&server&needs&to&obtain&these&public&keys&in&a&secure&way.&Ce
rtificates&solve&this&&I'll&discuss&them&a&bit&later.
We'll&look&at&the&simple&case,&with&a&pair&of&programs&called&StrongClient&a
nd&StrongServer.&StrongClient&creates&a&timestamp&and&a&random&number&and&se
nds&them&along&with&the&user's&name&and&a&signature&to&the&server.&The&lengt
h&of&the&signature&is&sent&before&the&signature&itself,&just&as&it&was&with&
the&message&digest&login&examples.
The&main()&method&attempts&to&use&a&private&key&extracted&from&a&keystore.&T
he&keystore&location,&password,&alias,&and&private&key&password&are&all&comm
and-line&parameters.&For&this&to&work,&you'll&need&to&have&created&a&pair&of
&DSA&keys&in&a&keystore&somewhere.&See&Chapter&5&if&you're&not&sure&how&to&d
import&java.io.*;
import&java.net.*;
import&java.security.*;
import&java.util.D
public&class&StrongClient&{
&&public&void&sendAuthentication(String&user,&PrivateKey&key,
&&&&&&OutputStream&outStream)&throws&IOException,&NoSuchAlgorithmException,
&&&&&&InvalidKeyException,&SignatureException&{
&&&&DataOutputStream&out&=&new&DataOutputStream(outStream);
&&&&long&t&=&(new&Date()).getTime();
&&&&double&q&=&Math.random();
&&&&Signature&s&=&Signature.getInstance("DSA");
&&&&s.initSign(key);
&&&&s.update(Protection.makeBytes(t,&q));
&&&&byte[]&signature&=&s.sign();
&&&&out.writeUTF(user);
&&&&out.writeLong(t);
&&&&out.writeDouble(q);
&&&&out.writeInt(signature.length);
&&&&out.write(signature);
&&&&out.flush();
&&public&static&void&main(String[]&args)&throws&Exception&{
&&&&if&(args.length&!=&5)&{
&&&&&&System.out.println(
&&&&&&&&&&"Usage:&StrongClient&host&keystore&storepass&alias&keypass");
&&&&String&host&=&args[0];
&&&&String&keystorefile&=&args[1];
&&&&String&storepass&=&args[2];
&&&&String&alias&=&args[3];
&&&&String&keypass&=&args[4];
&&&&int&port&=&7999;
&&&&Socket&s&=&new&Socket(host,&port);
&&&&StrongClient&client&=&new&StrongClient();
&&&&KeyStore&keystore&=&KeyStore.getInstance();
&&&&keystore.load(new&FileInputStream(keystorefile),&storepass);
&&&&PrivateKey&key&=&keystore.getPrivateKey(alias,&keypass);
client.sendAuthentication(alias,&key,&s.getOutputStream());
&&&&s.close();
The&server&version&of&this&program&simply&reads&the&information&from&the&str
eam&and&verifies&the&given&signature,&using&a&public&key&from&the&keystore&n
amed&in&the&command&line.&Note&that&the&client&sends&the&alias&name&to&the&s
erver.&This&implies&that&the&correct&keys&must&be&referenced&by&the&same&ali
as&in&both&the&keystore&that&the&client&uses&and&the&keystore&that&the&serve
import&java.io.*;
import&java.net.*;
import&java.security.*;
public&class&StrongServer&{
&&protected&KeyStore&mKeyS
&&public&StrongServer(KeyStore&keystore)&{&mKeyStore&=&&}
&&public&boolean&authenticate(InputStream&inStream)
&&&&&&throws&IOException,&NoSuchAlgorithmException,
&&&&&&InvalidKeyException,&SignatureException&{
&&&&DataInputStream&in&=&new&DataInputStream(inStream);
&&&&String&user&=&in.readUTF();
&&&&long&t&=&in.readLong();
&&&&double&q&=&in.readDouble();
&&&&int&length&=&in.readInt();
&&&&byte[]&signature&=&new&byte[length];
&&&&in.readFully(signature);
&&&&Signature&s&=&Signature.getInstance("DSA");
&&&&s.initVerify(mKeyStore.getCertificate(user).getPublicKey());
&&&&s.update(Protection.makeBytes(t,&q));
&&&&return&s.verify(signature);
&&public&static&void&main(String[]&args)&throws&Exception&{
&&&&if&(args.length&!=&2)&{
&&&&&&System.out.println("Usage:&StrongServer&keystore&storepass");
&&&&String&keystorefile&=&args[0];
&&&&String&storepass&=&args[1];
&&&&int&port&=&7999;
&&&&ServerSocket&s&=&new&ServerSocket(port);
&&&&Socket&client&=&s.accept();
&&&&KeyStore&keystore&=&KeyStore.getInstance();
&&&&keystore.load(new&FileInputStream(keystorefile),&storepass);
&&&&StrongServer&server&=&new&StrongServer(keystore);
&&&&if&(server.authenticate(client.getInputStream()))
&&&&&&System.out.println("Client&logged&in.");
&&&&&&System.out.println("Client&failed&to&log&in.");
&&&&s.close();
Run&the&server&by&pointing&it&to&the&keystore&you&wish&to&use,&as&follows:
C:\&java&StrongServer&c:\windows\.keystore&buendia
Then&run&the&client,&telling&it&the&server's&IP&address,&the&keystore&locati
on,&the&alias,&and&the&private&key&password.&Because&I'm&running&the&server&
and&client&on&the&same&machine,&I&use&localhost&for&the&server's&address:
C:\&java&StrongClient&localhost&c:\windows\.keystore&buendia&Jonathan
The&server&prints&a&message&indicating&if&the&client&logged&in.&Then&the&ser
ver&and&client&exit.
SignedObject
JDK&1.2&offers&a&utility&class,&java.security.SignedObject,&that&contains&an
y&Serializable&object&and&a&matching&signature.&You&can&construct&a&SignedOb
ject&with&a&Serializable&object,&a&private&key,&and&a&Signature:
public&SignedObject(Serializable&object,&PrivateKey&signingKey,&Signature&si
gningEngine)&throws&IOException,&InvalidKeyException,&SignatureException
This&constructor&creates&a&SignedObject&that&encapsulates&the&given&Serializ
able&object.&The&object&is&serialized&and&stored&internally.&The&serialized&
object&is&signed&using&the&supplied&Signature&and&private&key.
You&can&verify&the&signature&on&a&SignedObject&with&the&verify()&method:
public&final&boolean&verify(PublicKey&verificationKey,&Signature&verificatio
nEngine)&throws&InvalidKeyException,&SignatureException
This&method&verifies&that&the&SignedObject's&internal&signature&matches&its&
contained&object.&It&uses&the&supplied&public&key&and&Signature&to&perform&t
he&verification.&As&before,&the&Signature&does&not&need&to&be&initialized.&T
his&method&returns&true&if&the&SignedObject's&signature&matches&its&containe
d&&that&is,&the&contained&object's&integrity&is&verified.
You&can&retrieve&the&SignedObject's&contained&object&using&the&getObject()&m
public&Object&getObject()&throws&IOException,&ClassNotFoundException
This&method&returns&the&object&contained&in&this&SignedObject.&The&object&is
&stored&internally&as&a&byte&&this&method&deserializes&the&object&and&
returns&it.&To&be&assured&of&the&object's&integrity,&you&should&call&verify(
)&before&calling&this&method.
One&possible&application&of&SignedObject&is&in&the&last&example.&We&might&wr
ite&a&simple&class,&AuthorizationToken,&that&contained&the&user's&name,&the&
timestamp,&and&the&random&value.&This&object,&in&turn,&could&be&placed&insid
e&a&SignedObject&that&could&be&passed&from&client&to&server.
※&来源:·BBS&水木清华站&smth.org·[FROM:&162.105.18.201]
发信人:&Roland&(楼兰),&信区:&Java&&&&&&&
标&&题:&Java&MessageDigest&Example
发信站:&BBS&水木清华站&(Sat&Apr&15&10:34:13&2000)
The&first&challenge&of&building&a&secure&application&is&authentication.&Let
's&look&at&some&examples&of&authentication&from&everyday&life:
At&an&automated&bank&machine,&you&identify&yourself&using&your&bank&card.&Yo
u&authenticate&yourself&using&a&personal&identification&number&(PIN).&The&PI
N&is&a&shared&secret,&something&that&both&you&and&the&bank&know.&Presumably,
&you&and&the&bank&are&the&only&ones&who&know&this&number.
When&you&use&a&credit&card,&you&identify&yourself&with&the&card.&You&authent
icate&yourself&with&your&signature.&Most&store&clerks&never&check&the&signat &in&this&situation,&possession&of&the&card&is&authentication&enough.&Thi
s&is&true&when&you&order&something&over&the&telephone,&as&&simply&knowi
ng&the&credit&card&number&is&proof&of&your&identity.
When&you&rent&a&movie&at&a&video&store,&you&prove&your&identity&with&a&card&
or&by&saying&your&telephone&number.
Authentication&is&tremendously&important&in&computer&applications.&The&progr
am&or&person&you&communicate&with&may&be&in&the&next&room&or&on&another&cont &you&have&none&of&the&usual&visual&or&aural&clues&that&are&helpful&in&
everyday&transactions.&Public&key&cryptography&offers&some&powerful&tools&fo
r&proving&identity.
In&this&chapter,&I'll&describe&three&cryptographic&concepts&that&are&useful&
for&authentication:
Message&digests&produce&a&small&"fingerprint"&of&a&larger&set&of&data.
Digital&signatures&can&be&used&to&prove&the&integrity&of&data.
Certificates&are&used&as&cryptographically&safe&containers&for&public&keys.
A&common&feature&of&applications,&especially&custom-developed&"enterprise"&a
pplications,&is&a&login&window.&Users&have&to&authenticate&themselves&to&the
&application&before&they&use&it.&In&this&chapter,&we'll&examine&several&ways
&to&implement&this&with&cryptography.[1]&In&the&next&section,&for&instance,&
I'll&show&two&ways&to&use&a&message&digest&to&avoid&transmitting&a&password&
in&cleartext&from&a&client&to&a&server.&Later&on,&we'll&use&digital&signatur
es&instead&of&passwords.
Message&Digests
As&you&saw&in&Chapter&2,&Concepts,&a&message&digest&takes&an&arbitrary&amoun
t&of&input&data&and&produces&a&short,&digested&version&of&the&data.&The&Java
&Cryptography&Architecture&(JCA)&makes&it&very&easy&to&use&message&digests.&
The&java&.security.MessageDigest&class&encapsulates&a&cryptographic&message&
To&obtain&a&MessageDigest&for&a&particular&algorithm&use&one&of&its&getInsta
nce()&factory&methods:
public&static&MessageDigest&getInstance(String&algorithm)&throws&NoSuchAlgor
ithmException
This&method&returns&a&MessageDigest&for&the&given&algorithm.&The&first&provi
der&supporting&the&given&algorithm&is&used.
public&static&MessageDigest&getInstance(String&algorithm,&String&provider)&t
hrows&NoSuchAlgorithmException,&NoSuchProviderException
This&method&returns&a&MessageDigest&for&the&given&algorithm,&using&the&given
&provider.
To&feed&data&into&the&MessageDigest,&use&one&of&the&update()&methods:
public&void&update(byte&input)
This&method&adds&the&specified&byte&to&the&message&digest's&input&data.
public&void&update(byte[]&input)
Use&this&method&to&add&the&entire&input&array&to&the&message&digest's&input&
public&void&update(byte[]&input,&int&offset,&int&len)
This&method&adds&len&bytes&of&the&given&array,&starting&at&offset,&to&the&me
ssage&digest's&input&data.
You&can&call&the&update()&methods&as&many&times&as&you&want&before&calculati
ng&the&digest&value.
To&find&out&the&digest&value,&use&one&of&the&digest()&methods:
public&byte[]&digest()
The&value&of&the&message&digest&is&returned&as&a&byte&array.
public&byte[]&digest(byte[]&input)
This&method&is&provided&for&convenience.&It&is&equivalent&to&calling&update(
input),&followed&by&digest().
If&you&use&a&MessageDigest&to&calculate&a&digest&value&for&one&set&of&input&
data,&you&can&reuse&the&MessageDigest&for&a&second&set&of&data&by&clearing&i
ts&internal&state&first.
public&void&reset()
This&method&clears&the&internal&state&of&the&MessageDigest.&It&can&then&be&u
sed&to&calculate&a&new&digest&value&for&an&entirely&new&set&of&input&data.
One,&Two,&Three!
Thus,&you&can&calculate&a&message&digest&value&for&any&input&data&with&just&
a&few&lines&of&code:
//&Define&byte[]&inputData&first.
MessageDigest&md&=&MessageDigest.getInstance("SHA");
md.update(inputData);
byte[]&digest&=&md.digest();
Message&digests&are&one&of&the&building&blocks&of&digital&signatures.&Messag
e&digests&alone,&however,&can&be&useful,&as&you'll&see&in&the&following&sect
Digest&Streams
The&java.security&package&comes&with&two&classes&that&make&it&easy&to&calcul
ate&message&digests&on&stream&data.&These&classes&are&DigestInputStream&and&
DigestOutputStream,&descendants&of&the&FilterInputStream&and&FilterOutputStr
eam&classes&in&java.io.
Let's&apply&DigestInputStream&to&the&Masher&class&from&Chapter&1,&Introducti
on.&In&that&class,&we&read&a&file&and&calculated&its&message&digest&value&as
&&&&//&Obtain&a&message&digest&object.
&&&&MessageDigest&md&=&MessageDigest.getInstance("MD5");
&&&&//&Calculate&the&digest&for&the&given&file.
&&&&FileInputStream&in&=&new&FileInputStream(args[0]);
&&&&byte[]&buffer&=&new&byte[8192];
&&&&while&((length&=&in.read(buffer))&!=&-1)
&&&&&&&&md.update(buffer,&0,&length);
&&&&byte[]&raw&=&md.digest();
Now&let's&wrap&a&DigestInputStream&around&the&FileInputStream,&as&follows.&A
s&we&read&data&from&the&file,&the&MessageDigest&will&automatically&be&update
d.&All&we&need&to&do&is&read&the&entire&file.
&&&&//&Obtain&a&message&digest&object.
&&&&MessageDigest&md&=&MessageDigest.getInstance("MD5");
&&&&//&Calculate&the&digest&for&the&given&file.
&&&&DigestInputStream&in&=&new&DigestInputStream(
&&&&&&&&new&FileInputStream(args[0]),&md);
&&&&byte[]&buffer&=&new&byte[8192];
&&&&while&(in.read(buffer)&!=&-1)
&&&&byte[]&raw&=&md.digest();
DigestOutputStream&works&the&same&&all&bytes&written&to&the&stream&are&a
utomatically&passed&to&the&MessageDigest.
Protected&Password&Login
A&basic&problem&in&client/server&applications&is&that&the&server&wants&to&kn
ow&who&its&clients&are.&In&a&password-based&scheme,&the&client&prompts&the&u
ser&for&his&or&her&name&and&password.&The&client&relays&this&information&to&
the&server.&The&server&checks&the&name&and&password&and&either&allows&the&us
er&into&the&system&or&denies&access.&The&password&is&a&shared&secret&because
&both&the&user&and&the&server&must&know&it.&The&obvious&solution&is&to&send&
the&user's&name&and&password&directly&to&the&server.&Most&computer&networks,
&however,&are&highly&susceptible&to&eavesdropping,&so&this&is&not&a&very&sec
ure&solution.
To&avoid&passing&a&cleartext&password&from&client&to&server,&you&can&send&a&
message&digest&of&the&password&instead.&The&server&can&create&a&message&dige
st&of&its&copy&of&the&password.&If&the&two&message&digests&are&equal,&then&t
he&client&is&authenticated.&This&simple&procedure,&however,&is&vulnerable&to
&a&replay&attack.&A&malicious&user&could&listen&to&the&digested&password&and
&replay&it&later&to&gain&illicit&access&to&the&server.&To&avoid&this&problem
,&some&session-specific&information&is&added&to&the&message&digest.&In&parti
cular,&the&client&generates&a&random&number&and&a&timestamp&and&includes&the
m&in&the&digest.&These&values&must&also&be&sent,&in&the&clear,&to&the&server
,&so&that&the&server&can&use&them&to&calculate&a&matching&digest&value.&The&
server&must&be&programmed&to&receive&the&extra&information&and&include&it&in
&its&message&digest&calculations.&Figure&6-1&shows&how&this&works&on&the&cli
Figure&6-1.&Protecting&a&password
The&server&uses&the&given&name&to&look&up&the&password&in&a&private&database
.&Then&it&uses&the&given&name,&random&number,&timestamp,&and&the&password&it
&just&retrieved&to&calculate&a&message&digest.&If&this&digest&value&matches&
the&digest&sent&by&the&client,&the&client&has&been&authenticated.
The&following&program&shows&the&procedure&from&the&client's&point&of&view:
import&java.io.*;
import&java.net.*;
import&java.security.*;
import&java.util.D
public&class&ProtectedClient&{
&&public&void&sendAuthentication(String&user,&String&password,
&&&&&&OutputStream&outStream)&throws&IOException,&NoSuchAlgorithmException&{
&&&&DataOutputStream&out&=&new&DataOutputStream(outStream);
&&&&long&t1&=&(new&Date()).getTime();
&&&&double&q1&=&Math.random();
&&&&byte[]&protected1&=&Protection.makeDigest(user,&password,&t1,&q1);
&&&&out.writeUTF(user);
&&&&out.writeLong(t1);
&&&&out.writeDouble(q1);
&&&&out.writeInt(protected1.length);
&&&&out.write(protected1);
&&&&out.flush();
public&static&void&main(String[]&args)&throws&Exception&{
&&&&String&host&=&args[0];
&&&&int&port&=&7999;
&&&&String&user&=&"Jonathan";
&&&&String&password&=&"buendia";
&&&&Socket&s&=&new&Socket(host,&port);
&&&&ProtectedClient&client&=&new&ProtectedClient();
&&&&client.sendAuthentication(user,&password,&s.getOutputStream());
&&&&s.close();
The&bulk&of&the&algorithm&is&in&the&SendAuthentication()&method,&in&these&li
&&&&out.writeUTF(user);
&&&&out.writeLong(t1);
&&&&out.writeDouble(q1);
&&&&out.writeInt(protected1.length);
&&&&out.write(protected1);
Here&we&write&the&user&string,&timestamp,&and&random&number&as&cleartext.&In
stead&of&writing&the&message&digest&right&away,&we&first&write&out&its&lengt
h.&This&makes&it&easier&for&the&server&to&read&the&message&digest.&Although&
we&could&code&the&server&to&always&read&a&20-byte&SHA&digest,&we&might&decid
e&to&change&algorithms&some&time&in&the&future.&Writing&the&digest&length&in
to&the&stream&means&we&don't&have&to&worry&about&the&length&of&the&digest,&w
hatever&algorithm&we&use.
Also&note&that&ProtectedClient&is&not&Socket-specific.&You&could&use&it&to&w
rite&authentication&information&to&a&file&or&an&email&message.
Some&of&the&digestion&that&ProtectedClient&performs&will&be&mirrored&in&the&
server&class.&Therefore,&ProtectedClient's&sendAuthentication()&method&uses&
a&static&utility&method,&makeDigest(),&that&is&defined&in&the&Protection&cla
ss.&This&class&is&shown&below:
import&java.io.*;
import&java.security.*;
public&class&Protection&{
&&public&static&byte[]&makeDigest(String&user,&String&password,
&&&&&&long&t1,&double&q1)&throws&NoSuchAlgorithmException&{
&&&&MessageDigest&md&=&MessageDigest.getInstance("SHA");
&&&&md.update(user.getBytes());
&&&&md.update(password.getBytes());
&&&&md.update(makeBytes(t1,&q1));
&&&&return&md.digest();
&&public&static&byte[]&makeBytes(long&t,&double&q)&{
&&&&&&ByteArrayOutputStream&byteOut&=&new&ByteArrayOutputStream();
&&&&&&DataOutputStream&dataOut&=&new&DataOutputStream(byteOut);
&&&&&&dataOut.writeLong(t);
&&&&&&dataOut.writeDouble(q);
&&&&&&return&byteOut.toByteArray();
&&&&catch&(IOException&e)&{
&&&&&&return&new&byte[0];
Protection&defines&two&static&methods.&The&makeDigest()&method&creates&a&mes
sage&digest&from&its&input&data.&It&uses&a&helper&method,&makeBytes(),&whose
&purpose&is&to&convert&a&long&and&a&double&into&an&array&of&bytes.
On&the&server&side,&the&process&is&similar.&The&ProtectedServer&class&has&a&
method,&lookupPassword(),&that&returns&the&password&of&a&supplied&user.&In&o
ur&implementation,&it&is&hardcoded&to&return&one&password.&In&a&real&applica
tion,&this&method&would&probably&connect&to&a&database&or&a&password&file&to
&find&the&user's&password.
import&java.io.*;
import&java.net.*;
import&java.security.*;
public&class&ProtectedServer&{
&&public&boolean&authenticate(InputStream&inStream)
&&&&&&throws&IOException,&NoSuchAlgorithmException&{
&&&&DataInputStream&in&=&new&DataInputStream(inStream);
&&&&String&user&=&in.readUTF();
&&&&long&t1&=&in.readLong();
&&&&double&q1&=&in.readDouble();
&&&&int&length&=&in.readInt();
&&&&byte[]&protected1&=&new&byte[length];
&&&&in.readFully(protected1);
&&&&String&password&=&lookupPassword(user);
&&&&byte[]&local&=&Protection.makeDigest(user,&password,&t1,&q1);
&&&&return&MessageDigest.isEqual(protected1,&local);
&&protected&String&lookupPassword(String&user)&{&return&"buendia";&}
&&public&static&void&main(String[]&args)&throws&Exception&{
&&&&int&port&=&7999;
&&&&ServerSocket&s&=&new&ServerSocket(port);
&&&&Socket&client&=&s.accept();
&&&&ProtectedServer&server&=&new&ProtectedServer();
&&&&if&(server.authenticate(client.getInputStream()))
&&&&&&System.out.println("Client&logged&in.");
&&&&&&System.out.println("Client&failed&to&log&in.");
&&&&s.close();
To&test&the&protected&password&login,&first&start&up&the&server:
C:\&java&ProtectedServer
Then&run&the&client,&pointing&it&to&the&machine&where&the&server&is&running.
&I&run&both&these&programs&on&the&same&machine,&so&I&type&this&in&a&differen
t&command-line&window:
C:\&java&ProtectedClient&localhost
The&server&will&print&out&a&message&indicating&whether&the&client&logged&in.
&Then&both&programs&exit.
Double-Strength&Password&Login
There&is&a&stronger&method&for&protecting&password&information&using&message
&digests.&It&involves&an&additional&timestamp&and&random&number,&as&shown&in
&Figure&6-2.
Figure&6-2.&A&doubly&protected&password
First,&a&digest&is&computed,&just&as&in&the&previous&example.&Then,&the&dige
st&value,&another&random&number,&and&another&timestamp&are&fed&into&a&second
&digest.&Then&the&server&is&sent&the&second&digest&value,&along&with&the&tim
estamps&and&random&numbers.
Why&is&this&better&than&the&simpler&scheme&we&outlined&earlier?&To&understan
d&why,&think&about&how&you&might&try&to&break&the&protected&password&scheme.
&Recall&that&a&message&digest&is&a&one-way&&ideally,&this&means&tha
t&it's&impossible&to&figure&out&what&input&produced&a&given&digest&value.[2]
&Thus,&your&best&bet&is&to&launch&a&dictionary&attack.&This&means&that&you&t
ry&passwords,&one&at&a&time,&running&them&through&the&simple&protection&algo
rithm&just&described&and&attempting&to&log&in&each&time.&In&this&process,&it
's&important&to&consider&how&much&time&it&takes&to&test&a&single&password.&I
n&the&double-strength&protection&scheme,&two&digest&values&must&be&computed&
instead&of&just&one,&which&should&double&the&time&required&for&a&dictionary&
We&can&implement&the&double&protection&scheme&with&a&few&minimal&changes&to&
the&ProtectedClient&and&ProtectedServer&classes.&First,&ProtectedClient's&se
ndAuthentication()&method&needs&some&additional&logic.&The&new&lines&are&sho
wn&in&bold.
&&public&void&sendAuthentication(String&user,&String&password,
&&&&&&OutputStream&outStream)&throws&IOException,&NoSuchAlgorithmException&{
&&&&DataOutputStream&out&=&new&DataOutputStream(outStream);
&&&&long&t1&=&(new&Date()).getTime();
&&&&double&q1&=&Math.random();
&&&&byte[]&protected1&=&Protection.makeDigest(user,&password,&t1,&q1);
&&&&long&t2&=&(new&Date()).getTime();
&&&&double&q2&=&Math.random();
&&&&byte[]&protected2&=&Protection.makeDigest(protected1,&t2,&q2);
&&&&out.writeUTF(user);
&&&&out.writeLong(t1);
&&&&out.writeDouble(q1);
&&&&out.writeLong(t2);
&&&&out.writeDouble(q2);
&&&&out.writeInt(protected2.length);
&&&&out.write(protected2);
&&&&out.flush();
You&probably&noticed&that&there's&a&new&helper&method&in&the&Protection&clas
s.&It&takes&a&message&digest&value&(an&array&of&bytes),&a&timestamp,&and&a&r
andom&number&and&generates&a&new&digest&value.&This&new&static&method&in&the
&Protection&class&is&shown&next:
&&public&static&byte[]&makeDigest(byte[]&mush,&long&t2,&double&q2)
&&&&&&throws&NoSuchAlgorithmException&{
&&&&MessageDigest&md&=&MessageDigest.getInstance("SHA");
&&&&md.update(mush);
&&&&md.update(makeBytes(t2,&q2));
&&&&return&md.digest();
Finally,&the&server&needs&to&be&updated&to&accept&the&additional&protection&
information.&ProtectedServer's&modified&authenticate()&method&is&shown&here,
&with&the&new&lines&indicated&in&bold:
&&public&boolean&authenticate(InputStream&inStream)
&&&&&&throws&IOException,&NoSuchAlgorithmException&{
&&&&DataInputStream&in&=&new&DataInputStream(inStream);
&&&&String&user&=&in.readUTF();
&&&&long&t1&=&in.readLong();
&&&&double&q1&=&in.readDouble();
&&&&long&t2&=&in.readLong();
&&&&double&q2&=&in.readDouble();
&&&&int&length&=&in.readInt();
&&&&byte[]&protected2&=&new&byte[length];
&&&&in.readFully(protected2);
&&&&String&password&=&lookupPassword(user);
&&&&byte[]&local1&=&Protection.makeDigest(user,&password,&t1,&q1);
&&&&byte[]&local2&=&Protection.makeDigest(local1,&t2,&q2);
&&&&return&MessageDigest.isEqual(protected2,&local2);
Neither&the&regular&or&double-strength&login&methods&described&here&prevent&
a&dictionary&attack&on&the&password.&For&a&method&that&does&prevent&a&dictio
nary&attack,&see&http://srp.stanford.edu/srp/.
※&来源:·BBS&水木清华站&smth.org·[FROM:&162.105.18.201]
发信人:&Roland&(叶开不是傅红雪),&信区:&Disco
标&&题:&[新人]Roland前来Disco报到
发信站:&BBS&水木清华站&(Thu&Jun&17&20:39:52&2004),&站内
我是Roland,我前来
&&&&&&&&&&&&&&_______█◣&&&●&&&◢██◣&&◢██◣&&◢██◣&&&&&&&&&&&&&&&
&&&&&&&&&&&&&&&&&◢███&&▅◣&&███◥&&███◤&&██◤█&&&&&&&&&&&&&&&
&&&&&&&&&&&&&&&&&█◤◢█__██__◥██◣__███◢__██◢█______&&&&&&&&&
&&&&&&&&&&&&&&&&&◥██◤&&█◤&&◥▆▆◤&&◥██◤&&◥██◤&&&&&&&&&&&&&&&
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&报到了
你们叫我Roland就可以了
我原来没怎么玩过Disco诶~不知道我这么理解Disco可以不可以:
不会跳，想学
如果版面上组织活动的话,我要不要参加呢?
只是我自己也不太会啊~我想请个人教我,就找
都不认识。。。有自愿教我的么？
你可一定要教我教到会啊!
好了,最后向大家问声好吧:
┌────╮&&&&&&&&&&&&┌─┐&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&╭─╮
│█◤◥◣│╭────╮│█│&&&&&&╭────╮┌─╭──╮╭──╯█│
│█┌◢◤││◢◤◥◣││█│&&&&&&│◢◤◥◣││█◢█◣││◢◤◥█│
│█◤◣╭╯│█╭╯█││█└──╮│█╭╯█││█◤╮█││█╭╯█│
│█│◥█││◥◣◢◤││████││◥◣◢◥││█││█││◥◣◢◥│
└─┘╰─┘╰────╯└────╯╰───╰┘└─┘└─┘╰───╰┘
※&来源:·BBS&水木清华站&smth.org·[FROM:&219.224.146.*]
发信人:&Roland&(戒烟！为了Lp),&信区:&CStrike
标&&题:&[考核报告]U-V70
发信站:&BBS&水木清华站&(Tue&Sep&&9&23:44:59&2003),&转信
考核对象：windo&&&&U-V70
地图&de_aztec(没想到server没有bs地图。。。)
m4：pass&肉比较准，但是hs率偏低
ak：pass&hs率比m4高，但是瞄准似乎存在问题，除了hs之外，打肉的狠少
de：good&很准。。。。疟我了
awp：pass&站住位置之后帅枪很准，但是用awp的经验较少，而且不要开镜闪身
&&&&&移动过长的距离
总评：pass，可以参加diy继续锻炼，增加经验
（考核时server&down掉，因此考核的不很全面。。。。）
&&welcome&to&U&team~~~~~
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&U-Rol@nd
┌────╮&&&&&&&&&&&&┌─┐&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&╭─╮
│█◤◥◣│╭────╮│█│&&&&&&╭────╮┌─╭──╮╭──╯█│
│█┌◢◤││◢◤◥◣││█│&&&&&&│◢◤◥◣││█◢█◣││◢◤◥█│
│█◤◣╭╯│█╭╯█││█└──╮│█╭╯█││█◤╮█││█╭╯█│
│█│◥█││◥◣◢◤││████││◥◣◢◥││█││█││◥◣◢◥│
└─┘╰─┘╰────╯└────╯╰───╰┘└─┘└─┘╰───╰┘
※&修改:·Roland&于&Sep&&9&23:45:08&修改本文·[FROM:&&166.111.246.12]
※&修改:·Roland&于&Sep&&9&23:45:38&修改本文·[FROM:&&166.111.246.12]
※&来源:·BBS&水木清华站&smth.org·[FROM:&166.111.246.12]
发信人:&Roland&(雨过总会天晴),&信区:&CStrike
标&&题:&[考核报告]U-weijifen
发信站:&BBS&水木清华站&(Sun&Jul&&6&21:45:11&2003),&转信
map:&de_aztec&&&cs_bloodstrike
ak：good&远点很强，hs&rate也不错，不过近距离扫射需要加强
m4:pass&也是远距离比近距离好很多
mp5:good&认头很准，杀我的都是hs
handgun:pass&
awp:&pass&需要提高提前判断的意识
综合：good&需要多多联系近距离压枪的扫射
&&&&&&&练枪同时可以蹭蹭比赛提高经验
welcome&to&U&team~~~
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&U-Rol@nd
┌────╮&&&&&&&&&&&&┌─┐&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&╭─╮
│█◤◥◣│╭────╮│█│&&&&&&╭────╮┌─╭──╮╭──╯█│
│█┌◢◤││◢◤◥◣││█│&&&&&&│◢◤◥◣││█◢█◣││◢◤◥█│
│█◤◣╭╯│█╭╯█││█└──╮│█╭╯█││█◤╮█││█╭╯█│
│█│◥█││◥◣◢◤││████││◥◣◢◥││█││█││◥◣◢◥│
└─┘╰─┘╰────╯└────╯╰───╰┘└─┘└─┘╰───╰┘
※&修改:·Roland&于&Jul&&6&21:45:52&修改本文·[FROM:&166.111.161.132]
※&来源:·BBS&水木清华站&smth.org·[FROM:&166.111.161.132]
发信人:&Roland&(雨过总会天晴),&信区:&CStrike
标&&题:&[考核报告]U-bible
发信站:&BBS&水木清华站&(Sat&Jul&&5&22:07:28&2003),&转信
map:de_aztec&&&cs_bloodstrike
handgun:pass&和我的水平差不多，不过我的手枪很shit,不过没有用de和glock
mp5:good&认头很准
m4:pass&hs率偏低
ak:very&good&hs&rate&very&high&,ever&kill&me&by&5&continuous&hs
总评:good，可以开始打比赛蹭diy了
welcome&to&U&team~~~~
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&U-Rol@nd
┌────╮&&&&&&&&&&&&┌─┐&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&╭─╮
│█◤◥◣│╭────╮│█│&&&&&&╭────╮┌─╭──╮╭──╯█│
│█┌◢◤││◢◤◥◣││█│&&&&&&│◢◤◥◣││█◢█◣││◢◤◥█│
│█◤◣╭╯│█╭╯█││█└──╮│█╭╯█││█◤╮█││█╭╯█│
│█│◥█││◥◣◢◤││████││◥◣◢◥││█││█││◥◣◢◥│
└─┘╰─┘╰────╯└────╯╰───╰┘└─┘└─┘╰───╰┘
※&来源:·BBS&水木清华站&smth.org·[FROM:&166.111.161.132]
发信人:&Roland&(雨过总会天晴),&信区:&CStrike
标&&题:&[考核报告]U-Architect
发信站:&BBS&水木清华站&(Sat&Jun&21&00:55:48&2003),&转信
ak:pass&第一枪打肉很准，可是hs率偏低
m4:good&闪身点射很准，hs率也不错
map&bloodstrike
handgun：very&good&王子中的王子了，glock.usp.de都随便疟我没脾气,比你和我的ak
&&&&&&&&&m4的hs率加起来都高
ak:pass&&压枪时弹道控制不是很好，和自己m4比差些
m4:good&扫射很猛，很猛。。。
awp:pass&和我的差不多，考核的时候盲狙了我一枪很不错
mp5:good&移动很高，hs率也不低
综合&：good&&&短枪时移动意识不错，长枪蹲得有些死，而且移动时太有规律性
welcome&to&U&team~~~~
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&U-Rol@nd
┌────╮&&&&&&&&&&&&┌─┐&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&╭─╮
│█◤◥◣│╭────╮│█│&&&&&&╭────╮┌─╭──╮╭──╯█│
│█┌◢◤││◢◤◥◣││█│&&&&&&│◢◤◥◣││█◢█◣││◢◤◥█│
│█◤◣╭╯│█╭╯█││█└──╮│█╭╯█││█◤╮█││█╭╯█│
│█│◥█││◥◣◢◤││████││◥◣◢◥││█││█││◥◣◢◥│
└─┘╰─┘╰────╯└────╯╰───╰┘└─┘└─┘╰───╰┘
※&来源:·BBS&水木清华站&smth.org·[FROM:&166.111.160.201]
发信人:&Roland&(其实我有很多事情要做),&信区:&CStrike&&&&&&&
标&&题:&U-Rol@nd前来报道！
发信站:&BBS&水木清华站&(Mon&May&12&12:14:35&2003),&转信
还有U-27014
机器配置：烂
特点：rush不怕死，camp够ws
┌────╮&&&&&&&&&&&&┌─┐&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&╭─╮
│█◤◥◣│╭────╮│█│&&&&&&╭────╮┌─╭──╮╭──╯█│
│█┌◢◤││◢◤◥◣││█│&&&&&&│◢◤◥◣││█◢█◣││◢◤◥█│
│█◤◣╭╯│█╭╯█││█└──╮│█╭╯█││█◤╮█││█╭╯█│
│█│◥█││◥◣◢◤││████││◥◣◢◥││█││█││◥◣◢◥│
└─┘╰─┘╰────╯└────╯╰───╰┘└─┘└─┘╰───╰┘
※&修改:·Roland&于&May&12&12:17:10&修改本文·[FROM:&&166.111.161.71]
※&来源:·BBS&水木清华站&smth.org·[FROM:&166.111.161.71]
& NewSMTH.Net. The Selene Project.