(Visual Basic 6.0) Verify JWT with EdDSA / Ed25519 Signature

Note: This example requires Chilkat v9.5.0.84 or greater.

Demonstrates how to verify a JWT that was signed using an Ed25519 private key.

This example verifies the EdDSA signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original data.

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' Demonstrates how to verify a JWT with an EdDSA/Ed25519 Signature
' *** Requires Chilkat v9.5.0.84 or greater.

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' Use this Ed25519 public key for verification

Dim jsonPubKey As String
jsonPubKey = "{""kty"": ""OKP"",""alg"": ""EdDSA"",""crv"": ""Ed25519"",""x"": ""11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo""}"

Dim pubKey As New PublicKey
Dim success As Long
success = pubKey.LoadFromString(jsonPubKey)
If (success = 0) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Dim jwt As New ChilkatJwt
Dim token As String
token = "eyJhbGciOiJFZERTQSJ9.RXhhbXBsZSBvZiBFZDI1NTE5IHNpZ25pbmc.hgyY0il_MGCjP0JzlnLWG1PPOt7-09PGcvMg3AIbQR6dWbhijcNR4ki4iylGjg5BhVsPt9g7sVvpAr_MuM0KAg"

' First verify the signature.
Dim sigVerified As Long
sigVerified = jwt.VerifyJwtPk(token,pubKey)
Debug.Print "verified: " & sigVerified

If (sigVerified = 0) Then
    Debug.Print jwt.LastErrorText
    Exit Sub
End If

' Let's see if the time constraints, if any, are valid.
' The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
' If the current system time is before the "nbf" time, or after the "exp" time,
' then IsTimeValid will return false/0.
' Also, we'll allow a leeway of 60 seconds to account for any clock skew.
' Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
Dim leeway As Long
leeway = 60
Dim bTimeValid As Long
bTimeValid = jwt.IsTimeValid(token,leeway)
Debug.Print "time constraints valid: " & bTimeValid

' Recover the original data (the payload).
Dim payload As String
payload = jwt.GetPayload(token)
Debug.Print payload

' Recover the original JOSE header in the same way:
Dim joseHeader As String
joseHeader = jwt.GetHeader(token)
Debug.Print joseHeader