{
			queryParams: map[string]string{
				"Expires":        "60",
				"Signature":      "badsignature",
				"AWSAccessKeyId": accessKey,
			},
			expected: ErrExpiredPresignRequest,
		},
		// (4) Should error when the signature does not match.
		{
			queryParams: map[string]string{
				"Expires":        fmt.Sprintf("%d", now.Unix()+60),
				"Signature":      "badsignature",
				"AWSAccessKeyId": accessKey,
			},

	signature := calculateSignatureV2(stringToSign, cred.SecretKey)
	return signature
}

// compareSignatureV2 returns true if and only if both signatures
// are equal. The signatures are expected to be base64 encoded strings
// according to the AWS S3 signature V2 spec.
func compareSignatureV2(sig1, sig2 string) bool {
	// Decode signature string to binary byte-sequence representation is required

			return n, cr.err
		}
	}

	// Now, we read the signature of the following payload and expect:
	//   chunk-signature=" + <signature-as-hex> + "\r\n"
	//
	// The signature is 64 bytes long (hex-encoded SHA256 hash) and
	// starts with a 16 byte header: len("chunk-signature=") + 64 == 80.
	var signature [80]byte
	_, err = io.ReadFull(cr.reader, signature[:])
	if err == io.EOF {
		err = io.ErrUnexpectedEOF
	}

	if aec != ErrNone {
		return psv, aec
	}

	// Save signature.
	preSignV4Values.Signature, aec = parseSignature("Signature=" + query.Get(xhttp.AmzSignature))
	if aec != ErrNone {
		return psv, aec
	}

	// Return structured form of signature query string.
	return preSignV4Values, ErrNone
}

// Parses signature version '4' header of the following form.
//

			// validating the extraction/parsing of signature field.
			if !compareSignatureV4(testCase.expectedAuthField.Signature, parsedAuthField.Signature) {
				t.Errorf("Test %d: Parsed Signature field mismatch: Expected \"%s\", got \"%s\"", i+1, testCase.expectedAuthField.Signature, parsedAuthField.Signature)
			}

			// validating the extracted signed headers.

	}
	// List of readers used.
	readers := []io.Reader{
		// Test - 1
		bytes.NewReader([]byte("1000;chunk-signature=111123333333333333334444211\r\n")),
		// Test - 2
		bytes.NewReader([]byte("1000;")),
		// Test - 3
		bytes.NewReader(fmt.Appendf(nil, "%4097d", 1)),
		// Test - 4
		bytes.NewReader([]byte("1000;chunk-signature=111123333333333333334444211\r\n")),
	}
	testCases := []testCase{
		// Test - 1 - small bufio reader.
		{

            // Zero signature field for calculation
            for (int i = 0; i < SIGNATURE_LENGTH; i++) {
                data[SIGNATURE_OFFSET + i] = 0;
            }

            mac.update(data, 0, data.length);
            byte[] signature = mac.doFinal();

            // Place signature in data
            System.arraycopy(signature, 0, data, SIGNATURE_OFFSET, SIGNATURE_LENGTH);

    }

    /**
     * Gets the signature or authentication tag for the encrypted message
     *
     * @return the signature/authentication tag
     */
    public byte[] getSignature() {
        return this.signature;
    }

    /**
     * Sets the signature or authentication tag for the encrypted message
     *
     * @param signature
     *            the signature/authentication tag to set
     */

    }

    /**
     * Returns the server signature used to validate PAC integrity.
     * @return the server signature
     */
    public PacSignature getServerSignature() {
        return this.serverSignature;
    }

    /**
     * Returns the KDC signature used to validate PAC authenticity.
     * @return the KDC signature
     */
    public PacSignature getKdcSignature() {

    /**
     * Verifies the signature of this response.
     *
     * @param buffer the buffer containing the signature data
     * @param i the starting index in the buffer
     * @param size the size of the signature data
     * @return whether signature verification is successful
     */
    boolean verifySignature(byte[] buffer, int i, int size);

    /**
     * Checks if signature verification failed.
     *