aes_gcm_decryption java

aes_gcm_decryption.java

import javax.crypto.SecretKey;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.util.Arrays;
import java.util.Base64;

class Main {
  private final static int GCM_IV_LENGTH = 12;
  private final static int GCM_TAG_LENGTH = 16;

private static String decrypt(String encrypted, SecretKey skey) throws Exception {
    byte[] decoded = Base64.getDecoder().decode(encrypted);

    byte[] iv = Arrays.copyOfRange(decoded, 0, GCM_IV_LENGTH);

    Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
    GCMParameterSpec ivSpec = new GCMParameterSpec(GCM_TAG_LENGTH * Byte.SIZE, iv);
    
    cipher.init(Cipher.DECRYPT_MODE, skey, ivSpec);

    byte[] ciphertext = cipher.doFinal(decoded, GCM_IV_LENGTH, decoded.length - GCM_IV_LENGTH);

    String result = new String(ciphertext, "UTF8");
    System.out.println(result);
    return result;
}

  public static void main(String[] args) throws Exception {
    SecretKey key = new SecretKeySpec("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA".getBytes(), "AES");
    decrypt("SyiPupJTBm8I5+l2+VIyedKNRjLkJIj12dTsO7cCocMPl7JP9qoHIA==",key); // Got encrypted text from nodejs client (base64 encoded)
  }
}