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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.security.hpke;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
/**
* AES-128 GCM implementation of AEAD
*
* @author vekterli
*/
final class Aes128Gcm implements Aead {
private static final String AEAD_CIPHER_SPEC = "AES/GCM/NoPadding";
private static final Aes128Gcm INSTANCE = new Aes128Gcm();
public static Aes128Gcm getInstance() { return INSTANCE; }
/**
* @param key Symmetric key bytes for encryption/decryption
* @param nonce Nonce to use for the encryption/decrytion
* @param aad Associated authenticated data that will <em>not</em> be encrypted
* @param text Plaintext to seal or ciphertext to open, depending on cipherMode
* @return resulting ciphertext or plaintext, depending on cipherMode
*/
private byte[] aeadImpl(int cipherMode, byte[] key, byte[] nonce, byte[] aad, byte[] text) {
try {
var cipher = Cipher.getInstance(AEAD_CIPHER_SPEC);
var gcmSpec = new GCMParameterSpec(nT() * 8/* in bits */, nonce);
var aesKey = new SecretKeySpec(key, "AES");
cipher.init(cipherMode, aesKey, gcmSpec);
cipher.updateAAD(aad);
return cipher.doFinal(text);
} catch (NoSuchAlgorithmException | NoSuchPaddingException
| InvalidKeyException | InvalidAlgorithmParameterException
| IllegalBlockSizeException | BadPaddingException e) {
throw new RuntimeException(e);
}
}
@Override
public byte[] seal(byte[] key, byte[] nonce, byte[] aad, byte[] pt) {
return aeadImpl(Cipher.ENCRYPT_MODE, key, nonce, aad, pt);
}
@Override
public byte[] open(byte[] key, byte[] nonce, byte[] aad, byte[] ct) {
return aeadImpl(Cipher.DECRYPT_MODE, key, nonce, aad, ct);
}
@Override public short nK() { return 16; } // 128-bit key
@Override public short nN() { return 12; } // 96-bit IV
@Override public short nT() { return 16; } // 128-bit auth tag
@Override public short aeadId() { return 0x0001; } // AES-128-GCM
}
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