private static byte[] doHash(String text) throws SdkClientException {
        try {
            MessageDigest md = getMessageDigestInstance();
            md.update(text.getBytes(UTF8));
            return md.digest();
        } catch (Exception e) {
            throw new SdkClientException(
                    "Unable to compute hash while signing request: "
                            + e.getMessage(), e);
        }
    }
Hashes the string contents (assumed to be UTF-8) using the SHA-256
algorithm.

@param text
           The string to hash.

@return The hashed bytes from the specified string.

@throws SdkClientException
            If the hash cannot be computed.
aws-java-sdk-core/src/main/java/com/amazonaws/auth/AbstractAWSSigner.java