B4X Requires Chilkat v11.0.0+

Validate a JWS Using ECDSA P-256 SHA-256

See more JSON Web Signatures (JWS) Examples

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256 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-256", 
'        "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
'        "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
'       } 

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-256" & Chr(34) & ",")
sbPubKey.Append(Chr(34) & "x" & Chr(34) & ":" & Chr(34) & "f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU" & Chr(34) & ",")
sbPubKey.Append(Chr(34) & "y" & Chr(34) & ":" & Chr(34) & "x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" & 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("eyJhbGciOiJFUzI1NiJ9")
sbJws.Append(".")
sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt")
sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ")
sbJws.Append(".")
sbJws.Append("DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA")
sbJws.Append("pmWQxfKTUJqPP3-Kg6NU1Q")

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:

'  	Signature validated.
'  	--
'  	Recovered content:
'  	{"iss":"joe",
'  	 "exp":1300819380,
'  	 "http://example.com/is_root":true}
'  	--
'  	Protected (JOSE) header:
'  	{ 
'  	  "alg": "ES256"
'  	}