// Calculate signature.
	newSignature := getSignature(signingKey, stringToSign)

	// Verify if signature match.
	if !compareSignatureV4(newSignature, signV4Values.Signature) {
		return cred, "", "", time.Time{}, ErrSignatureDoesNotMatch
	}

	// Return calculated signature.
	return cred, newSignature, region, date, ErrNone
}

	// Get signing key.
	signingKey := getSigningKey(cred.SecretKey, credHeader.scope.date, credHeader.scope.region, serviceS3)

	// Get signature.
	newSignature := getSignature(signingKey, formValues.Get("Policy"))

	// Verify signature.
	if !compareSignatureV4(newSignature, formValues.Get(xhttp.AmzSignature)) {
		return cred, ErrSignatureDoesNotMatch
	}

	// Success.
	return cred, ErrNone
}