(Java) Verify an RSA Signature Against the Signed Hash

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Demonstrates how to validate an RSA Signature against the hash that was signed.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    CkBinData bd = new CkBinData();
    int i;
    for (i = 0; i <= 100; i++) {
        bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex");
        }

    String sha256_base64 = bd.getHash("sha256","base64");
    System.out.println("sha256 hash in base64 format: " + sha256_base64);

    String base64_rsa_sig = "AwF2BbOvL6jA5DwmMAc9n6J2Cc8PI6Rj5W079+aKJcIEtPWRzHor0Bvc3aftGM3Jbgj6SXlIC3M3RYS7UZOnfiHKFNZgbxaNT5WwsWooK42ZkC8DBZl0p7OunBUKd5SciUo+TKilioeUkriN3L1Zl9hwi3HVDVqgVo3XXskwIftSqLSFlepTLTmOWj9Y93dp8J4D9RyLtNgFQBc0WB22tyJTsuY56mLcWe1AMF3LizB9OrbwjynF2u16xWlrJdugccz795fJBUV9aQSD+8S3KeqwQhoi8RK1uhD68aGCyaSpBq0NZ8COAkn7MXaF4POxrAAt8udfHM+PRfSOptcH/w==";

    // Get the public key to be used for signature verification.
    CkPublicKey pubKey = new CkPublicKey();
    boolean success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem");
    if (success == false) {
        System.out.println(pubKey.lastErrorText());
        return;
        }

    CkRsa rsa = new CkRsa();
    rsa.ImportPublicKeyObj(pubKey);

    // Verify the hash against the signature.
    rsa.put_EncodingMode("base64");
    success = rsa.VerifyHashENC(sha256_base64,"sha256",base64_rsa_sig);

    if (success == false) {
        System.out.println(rsa.lastErrorText());
        System.out.println("Signature invalid.");
        }
    else {
        System.out.println("Signature valid.");
        }
  }
}