java使用Cipher进行签名和验签

public static void main(String[] args) {
try {
String plainText = "duwenlei";
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("rsa");
keyPairGenerator.initialize(2048);
KeyPair keyPair = keyPairGenerator.generateKeyPair(); //签名
MessageDigest md = MessageDigest.getInstance("sha1");
byte[] encHash = md.digest(plainText.getBytes());
PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyPair.getPrivate().getEncoded());
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
Key privateKey =keyFactory.generatePrivate(keySpec);
Cipher cipherSign = Cipher.getInstance(keyFactory.getAlgorithm());
cipherSign.init(Cipher.ENCRYPT_MODE,privateKey);
// cipherSign.init(Cipher.ENCRYPT_MODE,keyPair.getPrivate());
byte[] encHashSign = cipherSign.doFinal(encHash); //验签
X509EncodedKeySpec pkcs8EncodedKeySpec = new X509EncodedKeySpec(keyPair.getPublic().getEncoded());
KeyFactory keyFactoryPub = KeyFactory.getInstance("RSA");
Key publicKey = keyFactoryPub.generatePublic(pkcs8EncodedKeySpec);
Cipher cipherVer = Cipher.getInstance(keyFactoryPub.getAlgorithm());
cipherVer.init(Cipher.DECRYPT_MODE, publicKey);
// cipherVer.init(Cipher.DECRYPT_MODE, keyPair.getPublic());
byte[] decHashVer = cipherVer.doFinal(encHashSign);
MessageDigest md2 = MessageDigest.getInstance("sha1");
byte[] decHash = md2.digest(plainText.getBytes());// System.out.println("encHash = " + byte2hex(encHash));
// System.out.println("decHashVer = " + byte2hex(decHashVer));
// System.out.println("decHash = " + byte2hex(decHash));
System.out.println("签名是否正确：" + byte2hex(decHashVer).equals(byte2hex(decHash))); PEMWriter privateKeyWriter = new PEMWriter(new FileWriter(new File("D://privateKey.key")));
privateKeyWriter.writeObject(keyPair.getPrivate());
privateKeyWriter.flush();
privateKeyWriter.close();
PEMWriter publicKeyWriter = new PEMWriter(new FileWriter(new File("D://publicKey.key")));
publicKeyWriter.writeObject(keyPair.getPublic());
publicKeyWriter.flush();
publicKeyWriter.close();
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
} catch (IllegalBlockSizeException e) {
e.printStackTrace();
} catch (BadPaddingException e) {
e.printStackTrace();
} catch (InvalidKeySpecException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
public static byte[] hex2byte(String strhex) {
if (strhex == null) {
return null;
}
int l = strhex.length();
if (l % 2 == 1) {
return null;
}
byte[] b = new byte[l / 2];
for (int i = 0; i != l / 2; i++) {
b[i] = (byte) Integer.parseInt(strhex.substring(i * 2, i * 2 + 2),16);
}
return b;
} public static String byte2hex(byte[] b) {
String hs = "";
String stmp = "";
for (int n = 0; n < b.length; n++) {
stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));
if (stmp.length() == 1) {
hs = hs + "0" + stmp;
} else {
hs = hs + stmp ;
}
}
return hs.toUpperCase();
}