Example usage for org.bouncycastle.crypto.modes GCMBlockCipher processAADBytes

Introduction

In this page you can find the example usage for org.bouncycastle.crypto.modes GCMBlockCipher processAADBytes.

Prototype

public void processAADBytes(byte[] in, int inOff, int len) 

Source Link

Usage

From source file:com.github.horrorho.inflatabledonkey.crypto.AESGCM.java

License:Open Source License

/**
 * Returns decrypted data./* w w  w . java  2 s.  co  m*/
 *
 * @param key
 * @param nonce nonce/ IV
 * @param header
 * @param encryptedData
 * @param tag
 * @param optional optional AADBytes (post header)
 * @return decrypted data
 * @throws IllegalArgumentException on decryption exceptions
 * @throws NullPointerException on null arguments
 */
public static byte[] decrypt(byte[] key, byte[] nonce, byte[] header, byte[] encryptedData, byte[] tag,
        Optional<byte[]> optional) {

    try {
        GCMBlockCipher cipher = new GCMBlockCipher(new AESFastEngine());
        AEADParameters parameters = new AEADParameters(new KeyParameter(key), tag.length * 8, nonce, header);
        cipher.init(false, parameters);

        if (optional.isPresent()) {
            byte[] aadBytes = optional.get();
            cipher.processAADBytes(aadBytes, 0, aadBytes.length);
        }

        byte[] out = new byte[cipher.getOutputSize(encryptedData.length + tag.length)];

        int pos = cipher.processBytes(encryptedData, 0, encryptedData.length, out, 0);
        pos += cipher.processBytes(tag, 0, tag.length, out, pos);
        pos += cipher.doFinal(out, pos);

        return Arrays.copyOf(out, pos);

    } catch (IllegalStateException | InvalidCipherTextException ex) {
        throw new IllegalStateException("GCM decrypt error", ex);
    }
}

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