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You have to pass the correct length. Don't expect RPG to figure it out for you with %LEN (or %SIZE). The data isn't text, it's binary data. You need to know the length of the signature, and then pass that to base64_encode.

jonboy49 wrote: ↑Fri Jul 01, 2022 5:36 pm The signature length is being returned to by Qc3CalculateSignature. Any reason you cannot use that ?

Hello,
that was the problem, it's ok now.

Thank you so much for your help.

Best regards

I'm working jwt token for one of our vendor. since this post is related to JWT signature. I am trying to start the same thread..
I am struck at the signature part. I am able to convert the header and Payload (Claim set), I am unable to get the Signature part. I need help. I was using the same code provided by hmauricio. I am using the same Qc3CalculateSignature with signature is defined as ( dcl-s signature char(512) ccsid(*hex);)

I got the Private key converted from .PEM to .DAR in the keystore.
Here is my code for the signature..

BegSr $JWTSign;
keyDescription = *allx'00';
keyDescription.keystoreFile = 'KEYSTORE';
keyDescription.keystoreLibrary = '*LIBL';
keyDescription.recordLabel = 'PROS_PRICEAPI'; //PROS_PRICEAPI

algorithmDescription = *allx'00';
algorithmDescription.publicKeyCipherAlgorithm
= CRYPTO_ALGORITHM_RSA;
algorithmDescription.pkaBlockFormat = '1';
algorithmDescription.signingHashAlgorithm = HASH_ALGORITHM_SHA256;
Payload = %Trim($Rsp_Hdr) + '.'+ %Trim($Rsp_Clm);

Qc3CalculateSignature(
payload : %len(payload) : 'DATA0100' :
algorithmDescription : 'ALGD0400' :
keyDescription : 'KEYD0400' :
ANY_CRYPTO_SRV : '' :
signature : %size(signature) :
signatureLength : stdError );

// test code to to check what this code returns..
myBase64DataLen = apr_base64_encode_binary(myBase64Data
:signature
:signatureLength);
// would like to use this code..
myBase64DataLen = base64_encode(%addr(signature)
: signatureLength
: %addr(AsciiData)
: %size(AsciiData) );

$Rsp_Sign = %trim(AsciiData);

EndSr;
return $Rsp_Sign does not match the signature returned from jwt.io.
I need help here.

thanks
Ravi

I am able to fix the code.. thank you all