B4X

Verify JWT with EdDSA / Ed25519 Signature

See more JSON Web Token (JWT) Examples

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.

B4X

Dim success As Boolean = False

'  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 = "{" & Chr(34) & "kty" & Chr(34) & ": " & Chr(34) & "OKP" & Chr(34) & "," & Chr(34) & "alg" & Chr(34) & ": " & Chr(34) & "EdDSA" & Chr(34) & "," & Chr(34) & "crv" & Chr(34) & ": " & Chr(34) & "Ed25519" & Chr(34) & "," & Chr(34) & "x" & Chr(34) & ": " & Chr(34) & "11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo" & Chr(34) & "}"

Dim pubKey As ChilkatPublicKey
pubKey.Initialize
success = pubKey.LoadFromString(jsonPubKey)
If success = False Then
    Log(pubKey.LastErrorText)
    Return
End If


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

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

If sigVerified = False Then
    Log(jwt.LastErrorText)
    Return
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 Int = 60
Dim bTimeValid As Boolean = jwt.IsTimeValid(token, leeway)
Log("time constraints valid: " & bTimeValid)

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

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