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，然後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 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)創建證書並使用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()); 這裡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; }
