Bad Padding exception - RSA / ECB / OAEPWITHSHA-256ANDMGF1PADDING in pkcs11

Question

My application accesses an electronic token to decrypt the response coming from the server

The session key from the server is encrypted using: -

RSA / ECB / OAEPWITHSHA-256ANDMGF1PADDING

I am using the SunPKCS11 provider to implement access to crypto tokens. Whenever I try to decrypt this using the above mechanism, i.e. with RSA / ECB / OAEPWITHSHA-256ANDMGF1PADDING , I get: -

**javax.crypto.BadPaddingException: doFinal() failed  
    at sun.security.pkcs11.P11RSACipher.implDoFinal(P11RSACipher.java:328)  
    at sun.security.pkcs11.P11RSACipher.engineDoFinal(P11RSACipher.java:353)  
    at javax.crypto.Cipher.doFinal(DashoA13*..)

Below is my code: -

private static final String TRANSFORMATION = "RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING";
private static final String SECURITY_PROVIDER = "BC";
private static final String DIGEST_ALGORITHM = "SHA-256";
private static final String MASKING_FUNCTION = "MGF1";

The code fragment in which the error occurs looks as follows: -

private byte[] decryptSecretKeyData(byte[] encryptedSecretKey, byte[] iv, PrivateKey privateKey) throws Exception {

        try {
            Cipher rsaCipher = Cipher.getInstance(TRANSFORMATION, SECURITY_PROVIDER);

            System.out.println("Cipher block initialized"); - **Printed**
            PSource pSrc = (new PSource.PSpecified(iv));
            System.out.println("PSource inisitialized"); - **Printed**


            rsaCipher.init(Cipher.DECRYPT_MODE, privateKey,
                    new OAEPParameterSpec(DIGEST_ALGORITHM, MASKING_FUNCTION,
                            MGF1ParameterSpec.SHA256, pSrc));


            System.out.println("Here after cipher initilaization");  - **Not Printed***

            return rsaCipher.doFinal(encryptedSecretKey);
        } catch (GeneralSecurityException e) {
            System.out.println("GeneralSecurityException is "+e.getMessage());
            throw new Exception("Failed to decrypt AES secret key using RSA.", e);
        }
    }

I am stuck here and could not decrypt the OAEP transformation.

Answer 1

P11Key.P11PrivateKey . PKCS11, SunPKCS11 .

, SunPKCS11 OAEP, . BouncyCastle, SunPKCS11. keyLength - RSA (1024,2048 ..).

private void testEncryption(byte[] plainText, PrivateKey privateKey, PublicKey publicKey, int keyLength) throws GeneralSecurityException {

    System.out.println("Plain text: " + DatatypeConverter.printHexBinary(plainText));

    Provider bcProvider = new BouncyCastleProvider();
    Cipher rsaCipher = Cipher.getInstance("RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING", bcProvider);
    rsaCipher.init(Cipher.ENCRYPT_MODE, publicKey);
    byte[] cipherText = rsaCipher.doFinal(plainText);

    System.out.println("Cipher text: " + DatatypeConverter.printHexBinary(cipherText));

    Provider pkcs11provider = new SunPKCS11("C:\\Users\\manishs525\\pkcs11.cfg");
    Cipher rsaCipher2 = Cipher.getInstance("RSA/ECB/NoPadding", pkcs11provider);
    rsaCipher2.init(Cipher.DECRYPT_MODE, privateKey);
    byte[] paddedPlainText = rsaCipher2.doFinal(cipherText);

    /* Ensure leading zeros not stripped */
    if (paddedPlainText.length < keyLength / 8) {
        byte[] tmp = new byte[keyLength / 8];
        System.arraycopy(paddedPlainText, 0, tmp, tmp.length - paddedPlainText.length, paddedPlainText.length);
        System.out.println("Zero padding to " + (keyLength / 8));
        paddedPlainText = tmp;
    }           

    System.out.println("OAEP padded plain text: " + DatatypeConverter.printHexBinary(paddedPlainText));

    OAEPParameterSpec paramSpec = new OAEPParameterSpec("SHA-256", "MGF1", MGF1ParameterSpec.SHA1,
            PSource.PSpecified.DEFAULT);
    RSAPadding padding = RSAPadding.getInstance(RSAPadding.PAD_OAEP_MGF1, keyLength / 8, new SecureRandom(), paramSpec);
    byte[] plainText2 = padding.unpad(paddedPlainText);

    System.out.println("Unpadded plain text: " + DatatypeConverter.printHexBinary(plainText2));
}

:

• RSA/ECB/NoPadding SunPKCS11 JDK1.7.
• BouncyCastle 1.50 JDK 1.7

Answer 2

, , SunJCE Cipher " RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING" (BouncyCastle/IAIK/PKCS11)

AlgorithmParameters ( OAEPParameterSpec) (javax.crypto.BadPaddingException)

. "RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING"