Visual Basic 6.0

Compute a Public Key's JWK Thumbprint

Demonstrates the Chilkat PublicKey.GetJwkThumbprint method, which returns the RFC 7638 JWK thumbprint for the public key. The only argument is the hash algorithm (for example sha256).

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A JWK thumbprint is a canonical hash of the key's public parameters — a compact fingerprint that identifies the key regardless of formatting. It is the standard way to derive a stable key ID (kid) and to check whether two representations are the same key. Chilkat builds the required canonical JSON, hashes it with the named algorithm, and returns the result.

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Visual Basic 6.0

Dim success As Long
success = 0

'  Load a public key to export.  LoadFromFile inspects the content, so it accepts DER, PEM, XML,
'  JWK, and other supported representations.
Dim pubKey As New PublicKey
success = pubKey.LoadFromFile("qa_data/public.pem")
If (success = 0) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

'  Compute the RFC 7638 JWK thumbprint of the public key using the named hash algorithm.  Common
'  values include "sha256".
Dim thumbprint As String
thumbprint = pubKey.GetJwkThumbprint("sha256")
If (pubKey.LastMethodSuccess = 0) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Debug.Print "JWK thumbprint: " & thumbprint