(Excel) 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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Dim pubKey As Chilkat.PublicKey
Set pubKey = Chilkat.NewPublicKey

' 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...

Dim sb As Chilkat.StringBuilder
Set sb = Chilkat.NewStringBuilder
Dim success As Boolean
success = sb.Append("{")
success = sb.Append("""kty"": ""RSA"",")
success = sb.Append("""n"": ""0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAt")
success = sb.Append("VT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn6")
success = sb.Append("4tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FD")
success = sb.Append("W2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n9")
success = sb.Append("1CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINH")
success = sb.Append("aQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw"",")
success = sb.Append("""e"": ""AQAB"",")
success = sb.Append("""alg"": ""RS256"",")
success = sb.Append("""kid"": ""2011-04-29""")
success = sb.Append("}")

' The JWK format is automatically detected..

success = pubKey.LoadFromString(sb.GetAsString())
If (success <> True) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

' Get the JWK thumbprint (using SHA256)
Debug.Print "JWK thumbprint: "; pubKey.GetJwkThumbprint("SHA256")

' Output:
' JWK thumbprint: NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs

' --------------------------------------------------------------
' Now let's do an EC public key:
sb.Clear 
success = sb.Append("{ ")
success = sb.Append("  ""kty"": ""EC"",")
success = sb.Append("  ""crv"": ""P-256"",")
success = sb.Append("  ""x"": ""tDeeYABgKEAbWicYPCEEI8sP4SRIhHKcHDW7VqrB4LA"",")
success = sb.Append("  ""y"": ""J08HOoIZ0rX2Me3bNFZUltfxIk1Hrc8FsLu8VaSxsMI""")
success = sb.Append("}")

success = pubKey.LoadFromString(sb.GetAsString())
If (success <> True) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

' Get the JWK thumbprint (using SHA256)
Debug.Print "JWK thumbprint: "; pubKey.GetJwkThumbprint("SHA256")

' Output:
' JWK thumbprint: 8fm8079s3nu4FLV_7dVJoJ69A8XCXn7Za2mtaWCnxR4