(Tcl) Compute JWK Thumbprint for RSA and EC Public Keys

Demonstrates how to compute a JSON Web Key thumbprint for a public key (RSA or ECC).

Note: This example requires Chilkat v9.5.0.66 or greater.

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load ./chilkat.dll

set pubKey [new_CkPublicKey]

# A public key can be loaded from any format (binary DER, PEM, etc.)
# This example will load the public keys from JWK format, 
# and will then compute the JWK thumbprint.

# First do it for an RSA public key...

set sb [new_CkStringBuilder]

CkStringBuilder_Append $sb "{"
CkStringBuilder_Append $sb "\"kty\": \"RSA\","
CkStringBuilder_Append $sb "\"n\": \"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAt"
CkStringBuilder_Append $sb "VT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn6"
CkStringBuilder_Append $sb "4tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FD"
CkStringBuilder_Append $sb "W2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n9"
CkStringBuilder_Append $sb "1CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINH"
CkStringBuilder_Append $sb "aQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw\","
CkStringBuilder_Append $sb "\"e\": \"AQAB\","
CkStringBuilder_Append $sb "\"alg\": \"RS256\","
CkStringBuilder_Append $sb "\"kid\": \"2011-04-29\""
CkStringBuilder_Append $sb "}"

# The JWK format is automatically detected..
set success [CkPublicKey_LoadFromString $pubKey [CkStringBuilder_getAsString $sb]]
if {$success != 1} then {
    puts [CkPublicKey_lastErrorText $pubKey]
    delete_CkPublicKey $pubKey
    delete_CkStringBuilder $sb
    exit
}

# Get the JWK thumbprint (using SHA256)
puts "JWK thumbprint: [CkPublicKey_getJwkThumbprint $pubKey SHA256]"

# Output:
# JWK thumbprint: NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs

# --------------------------------------------------------------
# Now let's do an EC public key:
CkStringBuilder_Clear $sb
CkStringBuilder_Append $sb "{ "
CkStringBuilder_Append $sb "  \"kty\": \"EC\","
CkStringBuilder_Append $sb "  \"crv\": \"P-256\","
CkStringBuilder_Append $sb "  \"x\": \"tDeeYABgKEAbWicYPCEEI8sP4SRIhHKcHDW7VqrB4LA\","
CkStringBuilder_Append $sb "  \"y\": \"J08HOoIZ0rX2Me3bNFZUltfxIk1Hrc8FsLu8VaSxsMI\""
CkStringBuilder_Append $sb "}"

set success [CkPublicKey_LoadFromString $pubKey [CkStringBuilder_getAsString $sb]]
if {$success != 1} then {
    puts [CkPublicKey_lastErrorText $pubKey]
    delete_CkPublicKey $pubKey
    delete_CkStringBuilder $sb
    exit
}

# Get the JWK thumbprint (using SHA256)
puts "JWK thumbprint: [CkPublicKey_getJwkThumbprint $pubKey SHA256]"

# Output:
# JWK thumbprint: 8fm8079s3nu4FLV_7dVJoJ69A8XCXn7Za2mtaWCnxR4

delete_CkPublicKey $pubKey
delete_CkStringBuilder $sb