为什么我从RSA解密得到一个BadPadding异常？

Question

我用RSA算法加密和解密。当我加密一个字符串时，它工作正常。当我解密时，我得到一个错误。下面，我发布我的代码。

public final String modulusString ="..............";
public final String publicExponentString = "AQAB";

/* Encryption */
byte[] modulebytes = Base64.decode(modulusString);
byte[] exponentbytes = Base64.decode(publicExponentString);
BigInteger module = new BigInteger(1,modulebytes);
BigInteger publicexponent = new BigInteger(1,exponentbytes);
RSAPublicKeySpec rsaPubKey = new RSAPublicKeySpec(module, publicexponent);
KeyFactory fact = KeyFactory.getInstance("RSA");
PublicKey pubKey = fact.generatePublic(rsaPubKey);

Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);

byte[] plainBytes = EncryptionValue.getBytes("UTF-8");
byte[] cipherData = cipher.doFinal( plainBytes );
String encryptedString = Base64.encode(cipherData);

return encryptedString;

/* Decryption */
byte[] modulebytes = Base64.decode(modulusString);
byte[] exponentbytes = Base64.decode(publicExponentString);

BigInteger modulus = new BigInteger(1, modulebytes );
BigInteger exponent = new BigInteger(1, exponentbytes);

RSAPrivateKeySpec rsaPrivKey = new RSAPrivateKeySpec(modulus, exponent);
KeyFactory fact = KeyFactory.getInstance("RSA");
PrivateKey privKey = fact.generatePrivate(rsaPrivKey);

Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
cipher.init(Cipher.DECRYPT_MODE, privKey);

byte[] base64String = Base64.decode(DecryptionValue);
byte[] plainBytes = new String(base64String).getBytes("UTF-8");
plainBytes = cipher.update(plainBytes);
byte[] values = cipher.doFinal(plainBytes);

return new String(values, "UTF-8");

Exception in thread "main" javax.crypto.BadPaddingException: Decryption error
  at sun.security.rsa.RSAPadding.unpadV15(RSAPadding.java:380)
  at sun.security.rsa.RSAPadding.unpad(RSAPadding.java:291)
  at com.sun.crypto.provider.RSACipher.doFinal(RSACipher.java:363)
  at com.sun.crypto.provider.RSACipher.engineDoFinal(RSACipher.java:389)
  at javax.crypto.Cipher.doFinal(Cipher.java:2121)
  at cryptocodefinal.CryptoCodeFinal.DecryptionValue(CryptoCodeFinal.java:79)
  at cryptocodefinal.CryptoCodeFinal.main(CryptoCodeFinal.java:148)

Answer 1

您似乎正在使用公钥解密。那不行。您需要使用与用于加密的公共指数一起使用的私有指数进行解密。

没有私钥就无法解密。这就是非对称加密的要点。