I need to sign a request with AWS 4 but I am having issues with the Signature key.
From Amazon Doc
Use the digest (binary format) for the key derivation. Most languages have functions to compute either a binary format hash, commonly called a digest, or a hex-encoded hash, called a hexdigest. The key derivation requires that you use a binary-formatted digest.
Is it something that you are looking for?
byte printable = 'Rao'.bytes println printable def printableHex = printable.encodeHex() println printableHex.toString()