Update README.md for 1st start documentation

README.md

@@ -1,3 +1,27 @@
 
 # c2pa aws lambda sign demo with aws kms
 
+## Preperations for setup private key import for AWS KMS
+
+1. convert private key in binary format (.der)
+
+``
+openssl pkcs8 -topk8 -inform PEM -outform DER -in es256_private.key -out es256_private.der -nocrypt
+``
+
+2. Import with wrapping algorithm `RSAES_OAEP_SHA_256` and a RSA key 4096 bit, ref. [^1] 
+
+[^1]: https://docs.aws.amazon.com/kms/latest/developerguide/importing-keys-encrypt-key-material.html
+
+
+## Short Introduction in running c2patool with AWS KMS
+
+1. using parameter `signer-path`, ref [^3] and [^4]
+
+[^3]: https://github.com/contentauth/c2patool?tab=readme-ov-file#signing-claim-bytes-with-your-own-signer
+
+[^4]: https://github.com/nitrat7/c2pa_sign_awslambdakms/blob/main/lambda_c2pasign/runC2PA.cs#L208)
+
+2. and application that gets claim-bytes per standard-input and returns signed bytestream via standard-output, ref [^5]
+
+[^5]: https://github.com/nitrat7/c2pa_sign_awslambdakms/blob/main/kms_signer/Program.cs#L18