B4X Requires Chilkat v11.0.0+

Validate a JWS Using ECDSA P-521 SHA-512

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512 B4X

Dim success As Boolean = False

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

'  This example takes a JSON signature in compact serialization format,
'  and uses an ECDSA public key to validate and recover the protected header and payload.

'  We only need a public key for signature validation.  This is the ECDSA public key
'  that is used:

'       {"kty":"EC", 
'        "crv":"P-521", 
'        "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
'        "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
'       } 

Dim sbPubKey As ChilkatStringBuilder
sbPubKey.Initialize
sbPubKey.Append("{" & Chr(34) & "kty" & Chr(34) & ":" & Chr(34) & "EC" & Chr(34) & ",")
sbPubKey.Append(Chr(34) & "crv" & Chr(34) & ":" & Chr(34) & "P-521" & Chr(34) & ",")
sbPubKey.Append(Chr(34) & "x" & Chr(34) & ":" & Chr(34) & "AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk" & Chr(34) & ",")
sbPubKey.Append(Chr(34) & "y" & Chr(34) & ":" & Chr(34) & "ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" & Chr(34))
sbPubKey.Append("}")

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


Dim jws As ChilkatJws
jws.Initialize

'  Set the ECC public key:
Dim signatureIndex As Int = 0
jws.SetPublicKey(signatureIndex, pubKey)

'  Load the JWS.
Dim sbJws As ChilkatStringBuilder
sbJws.Initialize
sbJws.Append("eyJhbGciOiJFUzUxMiJ9")
sbJws.Append(".")
sbJws.Append("UGF5bG9hZA")
sbJws.Append(".")
sbJws.Append("AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq")
sbJws.Append("wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp")
sbJws.Append("EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn")

success = jws.LoadJwsSb(sbJws)
If success = False Then
    Log(jws.LastErrorText)
    Return
End If


'  Validate the 1st (and only) signature at index 0..
Dim v As Int = jws.Validate(signatureIndex)
If v < 0 Then
    '  Perhaps Chilkat was not unlocked or the trial expired..
    Log("Method call failed for some other reason.")
    Log(jws.LastErrorText)
    Return
End If

If v = 0 Then
    Log("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.")
    Return
End If


'  If we get here, the signature was validated..
Log("Signature validated.")
Log("--")

'  Recover the original content:
Log("Recovered content:")
Log(jws.GetPayload("utf-8"))
Log("--")

'  Examine the protected header:

Dim joseHeader As ChilkatJsonObject
joseHeader.Initialize
success = jws.GetProtectedH(signatureIndex, joseHeader)
If success = False Then
    Log(jws.LastErrorText)
    Return
End If


joseHeader.EmitCompact = False

Log("Protected (JOSE) header:")
Log(joseHeader.Emit)

'  Output:
'  (the string "Payload" was the content that was signed.)

'  	Signature validated.
'  	--
'  	Recovered content:
'  	Payload
'  	--
'  	Protected (JOSE) header:
'  	{
'  	  "alg": "ES512"
'  	}