Java生成RSA密钥对的两种方法：
1、RSAPublicKeySpec和RSAPrivateCrtKeySpec
这两个API是JAVA安全模块自带的API，可以查看API的相关说明：
public RSAPublicKeySpec(BigInteger modulus,BigInteger
publicExponent)
创建一个新的RSAPublicKeySpec。
参数
modulus - 模数
publicExponent - 公钥指数
publicRSAPrivateCrtKeySpec(BigInteger modulus,
BigIntegerpublicExponent,
BigInteger privateExponent,
BigInteger primeP,
BigInteger primeQ,
BigIntegerprimeExponentP,
BigIntegerprimeExponentQ,
BigInteger crtCoefficient)
创建一个新的RSAPrivateCrtKeySpec给定在PKCS＃1中定义的模数，publicExponent，privateExponent，primeP，primeQ，primeExponentP，primeExponentQ和crtCoefficient。
参数
modulus - 模数n
publicExponent - 公钥指数e
privateExponent -私钥指数d
primeP - n的素因子p
primeQ - n的素因子q
primeExponentP - 这是d mod（p-1）
primeExponentQ - 这是d mod（q-1）
crtCoefficient - 剩余定理系数q-1 mod p
示例代码如下：
// 创建指定公钥的对象
RSAPublicKeySpec localRSAPublicKeySpec1 =
new RSAPublicKeySpec(new
BigInteger("b4a7e46170574f16a97082b22be58b6a2a629798419be12872a4bdba626cfae9900f76abfb12139dce5de56564fab2b6543165a040c606887420e33d91ed7ed7",
16), new BigInteger("11", 16));
// 创建指定私钥的对象
RSAPrivateCrtKeySpec
localRSAPrivateCrtKeySpec1 = new RSAPrivateCrtKeySpec(new
BigInteger("b4a7e46170574f16a97082b22be58b6a2a629798419be12872a4bdba626cfae9900f76abfb12139dce5de56564fab2b6543165a040c606887420e33d91ed7ed7",
16), new BigInteger("11", 16), new
BigInteger("9f66f6b05410cd503b2709e88115d55daced94d1a34d4e32bf824d0dde6028ae79c5f07b580f5dce240d7111f7ddb130a7945cd7d957d1920994da389f490c89",
16), new
BigInteger("c0a0758cdf14256f78d4708c86becdead1b50ad4ad6c5c703e2168fbf37884cb",
16), new BigInteger("f01734d7960ea60070f1b06f2bb81bfac48ff192ae18451d5e56c734a5aab8a5",
16), new
BigInteger("b54bb9edff22051d9ee60f9351a48591b6500a319429c069a3e335a1d6171391",
16), new BigInteger("d3d83daf2a0cecd3367ae6f8ae1aeb82e9ac2f816c6fc483533d8297dd7884cd",
16), new BigInteger("b8f52fc6f38593dabb661d3f50f8897f8106eee68b1bce78a95b132b4e5b5d19",
16));
// 创建指定RSA算法的密钥工厂，指定工厂为BC
KeyFactory localKeyFactory =
KeyFactory.getInstance("RSA", "BC");
// 生成私钥
PrivateKey localPrivateKey1 =
localKeyFactory.generatePrivate(localRSAPrivateCrtKeySpec1);
// 生成公钥
PublicKey localPublicKey1 =
localKeyFactory.generatePublic(localRSAPublicKeySpec1);
2、KeyPair 和KeyPairGenerator
KeyPairGenerator类用于生成公钥和私钥对。 密钥对生成器使用getInstance工厂方法（返回给定类的实例的静态方法）构造。
用于特定算法的密钥对生成器创建可以与该算法一起使用的公钥/私钥对。 它还将算法特定的参数与生成的每个密钥相关联。
生成密钥对的方法有两种：以算法无关的方式，并以算法特定的方式。
publicKeyPair(PublicKey publicKey, PrivateKey privateKey)
从给定的公钥和私钥构造一个密钥对。
请注意，此构造函数仅存储对生成的密钥对中的公钥和私钥组件的引用。 这是安全的，因为Key对象是不可变的。
参数
publicKey - 公钥。
privateKey - 私钥。
示例代码如下：
// 生成RSA公私钥对
KeyPairGenerator kpg = null;
// 采用 RSA 非对称算法加密
kpg =KeyPairGenerator.getInstance("RSA");
// 初始化为2048 位
kpg.initialize(2048);
KeyPair keyPair = kpg.generateKeyPair();
// 公钥
PublicKey pubKey =localKeyFactory.generatePublic(localRSAPublicKeySpec1);
// 私钥
PrivateKey priKey = keyPair.getPrivate();
3、完整的示例代码
packagecom.test;
importjava.io.File;
importjava.io.FileOutputStream;
importjava.io.IOException;
importjava.math.BigInteger;
importjava.security.KeyPair;
importjava.security.KeyPairGenerator;
importjava.security.PrivateKey;
importjava.security.PublicKey;
importjava.security.Security;
importjava.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
importjava.util.Calendar;
importjava.util.Date;
importjava.util.Hashtable;
importjava.util.Vector;
importorg.bouncycastle.asn1.x509.KeyUsage;
importorg.bouncycastle.asn1.x509.X509Extension;
importorg.bouncycastle.jce.X509Principal;
importorg.bouncycastle.jce.provider.BouncyCastleProvider;
importorg.bouncycastle.x509.X509V3CertificateGenerator;
@SuppressWarnings("deprecation")
public class GenCrt {
/**
*BouncyCastleProvider
*/
static {
Security.addProvider(new BouncyCastleProvider());
}
/**
*生成 X509 证书
*@param user
*@return
*/
@SuppressWarnings({ "deprecation", "unchecked" })
public static byte[] generateCert() {
X509Certificatecert = null;
X509V3CertificateGeneratorcertGen=new X509V3CertificateGenerator();
try {
// 生成RSA公私钥对
KeyPairGeneratorkpg = null;
// 采用 RSA 非对称算法加密
kpg= KeyPairGenerator.getInstance("RSA");
// 初始化为2048 位
kpg.initialize(2048);
KeyPairkeyPair = kpg.generateKeyPair();
// 公钥
PublicKeypubKey = keyPair.getPublic();
// 私钥
PrivateKeypriKey = keyPair.getPrivate();
// 公钥
certGen.setPublicKey(pubKey);
// 设置序列号
certGen.setSerialNumber(new BigInteger("12345678"));
// 设置颁发者信息
@SuppressWarnings("rawtypes")
HashtablekwMapIssuer = new Hashtable();
@SuppressWarnings("rawtypes")
VectorlocalVector = new Vector();
kwMapIssuer.put(X509Principal.C,"CN");
localVector.addElement(X509Principal.C);
kwMapIssuer.put(X509Principal.CN,"wuwu");
localVector.addElement(X509Principal.CN);
kwMapIssuer.put(X509Principal.E, "[email protected]");
localVector.addElement(X509Principal.E);
certGen.setIssuerDN(new X509Principal(localVector, kwMapIssuer));
// 设置申请者信息
@SuppressWarnings("rawtypes")
HashtablekwMapApplicant = new Hashtable();
@SuppressWarnings("rawtypes")
VectorlocalVectorApplicant = new Vector();
kwMapApplicant.put(X509Principal.C,"CN");
localVectorApplicant.addElement(X509Principal.C);
kwMapApplicant.put(X509Principal.CN,"wlhl");
localVectorApplicant.addElement(X509Principal.CN);
kwMapApplicant.put(X509Principal.E, "[email protected]");
localVectorApplicant.addElement(X509Principal.E);
certGen.setSubjectDN(new X509Principal(localVectorApplicant, kwMapApplicant));
// 设置有效期
Calendarc= Calendar.getInstance();
c.set(Calendar.DAY_OF_YEAR, c.get(Calendar.DAY_OF_YEAR) + 7000);
certGen.setNotBefore(new Date());
certGen.setNotAfter(c.getTime());
// 设置扩展域，密钥用途
certGen.addExtension(X509Extension.keyUsage, false, new KeyUsage(KeyUsage.digitalSignature));
// 签名算法
certGen.setSignatureAlgorithm("SHA256WithRSAEncryption");
cert = certGen.generateX509Certificate(priKey, "BC");
}catch (Exception e) {
System.out.println(e.getClass() + e.getMessage());
}
try {
return cert.getEncoded();
}catch (CertificateEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
/**
*写文件
*@param name
*@param data
*/
static public void writeFile(String name, byte[] data) {
if(data == null)
{
return;
}
FileOutputStreamfop = null;
try {
fop = new FileOutputStream(new File(name));
fop.write(data);
fop.close();
}catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void main(String[] args) {
// TODOAuto-generated method stub
byte[] crtBuf=generateCert();
if(crtBuf != null) {
writeFile("./TestCrt.crt", crtBuf);
}
}
}
生成后的效果：
