JAVA對數字證書的常用操作
Java是一個面向對象的語言。對程序員來說，這意味著要注意應中的數據和操縱數據的方法(method)，而不是嚴格地用過程來思考。以下是關于JAVA對數字證書的常用操作，歡迎大家參考!
一：需要包含的包
import java.security. * ;
import java.io. * ;
import java.util. * ;
import java.security. * ;
import java.security.cert. * ;
import sun.security.x509. *
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
二：從文件中讀取證書
用keytool將.keystore中的證書寫入文件中，然后從該文件中讀取證書信息
CertificateFactory cf = CertificateFactory.getInstance( " X.509 " );
FileInputStream in = new FileInputStream( " out.csr " );
Certificate c = cf.generateCertificate(in);
String s = c.toString();
三：從密鑰庫中直接讀取證書
String pass = " 123456 " ;
FileInputStream in = new FileInputStream( " .keystore " );
KeyStore ks = KeyStore.getInstance( " JKS " );
ks.load(in,pass.toCharArray());
java.security.cert.Certificate c = ks.getCertificate(alias); // alias為條目的別名
四：JAVA程序中顯示證書指定信息
System.out.println( " 輸出證書信息:\n " + c.toString());
System.out.println( " 版本號: " + t.getVersion());
System.out.println( " 序列號: " + t.getSerialNumber().toString( 16 ));
System.out.println( " 主體名： " + t.getSubjectDN());
System.out.println( " 簽發者： " + t.getIssuerDN());
System.out.println( " 有效期： " + t.getNotBefore());
System.out.println( " 簽名算法： " + t.getSigAlgName());
byte [] sig = t.getSignature(); // 簽名值
PublicKey pk = t.getPublicKey();
byte [] pkenc = pk.getEncoded();
System.out.println( " 公鑰 " );
for ( int i = 0 ;i < pkenc.length;i ++ )System.out.print(pkenc[i] + " , " );
五：JAVA程序列出密鑰庫所有條目
String pass = " 123456 " ;
FileInputStream in = new FileInputStream( " .keystore " );
KeyStore ks = KeyStore.getInstance( " JKS " );
ks.load(in,pass.toCharArray());
Enumeration e = ks.aliases();
while (e.hasMoreElements())
java.security.cert.Certificate c = ks.getCertificate((String)e.nextElement());
六：JAVA程序修改密鑰庫口令
String oldpass = " 123456 " ;
String newpass = " 654321 " ;
FileInputStream in = new FileInputStream( " .keystore " );
KeyStore ks = KeyStore.getInstance( " JKS " );
ks.load(in,oldpass.toCharArray());
in.close();
FileOutputStream output = new FileOutputStream( " .keystore " );
ks.store(output,newpass.toCharArray());
output.close();
七：JAVA程序修改密鑰庫條目的口令及添加條目
FileInputStream in = new FileInputStream( " .keystore " );
KeyStore ks = KeyStore.getInstance( " JKS " );
ks.load(in,storepass.toCharArray());
Certificate [] cchain = ks.getCertificate(alias);獲取別名對應條目的證書鏈
PrivateKey pk = (PrivateKey)ks.getKey(alias,oldkeypass.toCharArray());獲取別名對應條目的私鑰
ks.setKeyEntry(alias,pk,newkeypass.toCharArray(),cchain);向密鑰庫中添加條目
第一個參數指定所添加條目的別名，假如使用已存在別名將覆蓋已存在條目，使用新別名將增加一個新條目，第二個參數為條目的私鑰，第三個為設置的新口令，第四個為該私鑰的公鑰的證書鏈
FileOutputStream output=new FileOutputStream("another");
ks.store(output,storepass.toCharArray())將keystore對象內容寫入新文件
八：JAVA程序檢驗別名和刪除條目
FileInputStream in = new FileInputStream( " .keystore " );
KeyStore ks = KeyStore.getInstance( " JKS " );
ks.load(in,storepass.toCharArray());
ks.containsAlias( " sage " );檢驗條目是否在密鑰庫中，存在返回true
ks.deleteEntry( " sage " );刪除別名對應的.條目
FileOutputStream output = new FileOutputStream( " .keystore " );
ks.store(output,storepass.toCharArray())將keystore對象內容寫入文件,條目刪除成功
九：JAVA程序簽發數字證書
(1)從密鑰庫中讀取CA的證書
FileInputStream in = new FileInputStream( " .keystore " );
KeyStore ks = KeyStore.getInstance( " JKS " );
ks.load(in,storepass.toCharArray());
java.security.cert.Certificate c1 = ks.getCertificate( " caroot " );
(2)從密鑰庫中讀取CA的私鑰
PrivateKey caprk = (PrivateKey)ks.getKey(alias,cakeypass.toCharArray());
(3)從CA的證書中提取簽發者的信息
byte [] encod1 = c1.getEncoded(); 提取CA證書的編碼
X509CertImpl cimp1 = new X509CertImpl(encod1); 用該編碼創建X509CertImpl類型對象
X509CertInfo cinfo1 = (X509CertInfo)cimp1.get(X509CertImpl.NAME + " . " + X509CertImpl.INFO); 獲取X509CertInfo對象
X500Name issuer = (X500Name)cinfo1.get(X509CertInfo.SUBJECT + " . " + CertificateIssuerName.DN_NAME); 獲取X509Name類型的簽發者信息
(4)獲取待簽發的證書
CertificateFactory cf = CertificateFactory.getInstance( " X.509 " );
FileInputStream in2 = new FileInputStream( " user.csr " );
java.security.cert.Certificate c2 = cf.generateCertificate(in);
(5)從待簽發的證書中提取證書信息
byte [] encod2 = c2.getEncoded();
X509CertImpl cimp2 = new X509CertImpl(encod2); 用該編碼創建X509CertImpl類型對象
X509CertInfo cinfo2 = (X509CertInfo)cimp2.get(X509CertImpl.NAME + " . " + X509CertImpl.INFO); 獲取X509CertInfo對象
(6)設置新證書有效期
Date begindate = new Date(); 獲取當前時間
Date enddate = new Date(begindate.getTime() + 3000 * 24 * 60 * 60 * 1000L ); 有效期為3000天
CertificateValidity cv = new CertificateValidity(begindate,enddate); 創建對象
cinfo2.set(X509CertInfo.VALIDITY,cv); 設置有效期
(7)設置新證書序列號
int sn = ( int )(begindate.getTime() / 1000 ); 以當前時間為序列號
CertificateSerialNumber csn = new CertificateSerialNumber(sn);
cinfo2.set(X509CertInfo.SERIAL_NUMBER,csn);
(8)設置新證書簽發者
cinfo2.set(X509CertInfo.ISSUER+"."+CertificateIssuerName.DN_NAME,issuer);應用第三步的結果
(9)設置新證書簽名算法信息
AlgorithmId algorithm=new AlgorithmId(AlgorithmId.md5WithRSAEncryption_oid);
cinfo2.set(CertificateAlgorithmId.NAME+"."+CertificateAlgorithmId.ALGORITHM,algorithm);
(10)創建證書并使用CA的私鑰對其簽名
X509CertImpl newcert=new X509CertImpl(cinfo2);
newcert.sign(caprk,"MD5WithRSA"); 使用CA私鑰對其簽名
(11)將新證書寫入密鑰庫
ks.setCertificateEntry( " lf_signed " ,newcert);
FileOutputStream out = new FileOutputStream( " newstore " );
ks.store(out, " newpass " .toCharArray()); 這里是寫入了新的密鑰庫，也可以使用第七條來增加條目
十：數字證書的檢驗
(1)驗證證書的有效期
(a)獲取X509Certificate類型對象
CertificateFactory cf = CertificateFactory.getInstance( " X.509 " );
FileInputStream in1 = new FileInputStream( " aa.crt " );
java.security.cert.Certificate c1 = cf.generateCertificate(in1);
X509Certificate t = (X509Certificate)c1;
in2.close();
(b)獲取日期
Date TimeNow=new Date();
(c)檢驗有效性
try {
t.checkValidity(TimeNow);
System.out.println( " OK " );
} catch (CertificateExpiredException e) { // 過期
System.out.println( " Expired " );
System.out.println(e.getMessage());
} catch ((CertificateNotYetValidException e) { // 尚未生效
System.out.println( " Too early " );
System.out.println(e.getMessage());}
(2)驗證證書簽名的有效性
(a)獲取CA證書
CertificateFactory cf = CertificateFactory.getInstance( " X.509 " );
FileInputStream in2 = new FileInputStream( " caroot.crt " );
java.security.cert.Certificate cac = cf.generateCertificate(in2);
in2.close();
(c)獲取CA的公鑰
PublicKey pbk=cac.getPublicKey();
(b)獲取待檢驗的證書(上步已經獲取了，就是C1)
(c)檢驗證書
boolean pass = false ;
try {
c1.verify(pbk);
pass = true ;
} catch (Exception e) {
pass = false ;
System.out.println(e);
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