B4X Requires Chilkat v11.0.0+

Create a JWS Using ECDSA P-256 SHA-256

See more JSON Web Signatures (JWS) Examples

Creates and 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.

'  Note: This example requires Chilkat v9.5.0.66 or greater.

'  Use the following ECC key loaded from JWK format.
Dim sbJwk As ChilkatStringBuilder
sbJwk.Initialize
sbJwk.Append("{" & Chr(34) & "kty" & Chr(34) & ":" & Chr(34) & "EC" & Chr(34) & ",")
sbJwk.Append(Chr(34) & "crv" & Chr(34) & ":" & Chr(34) & "P-256" & Chr(34) & ",")
sbJwk.Append(Chr(34) & "x" & Chr(34) & ":" & Chr(34) & "f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU" & Chr(34) & ",")
sbJwk.Append(Chr(34) & "y" & Chr(34) & ":" & Chr(34) & "x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" & Chr(34) & ",")
sbJwk.Append(Chr(34) & "d" & Chr(34) & ":" & Chr(34) & "jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI" & Chr(34))
sbJwk.Append("}")

Dim eccKey As ChilkatPrivateKey
eccKey.Initialize("eccKey")
'  Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
'  into the private key object. (See the online reference documentation..)
success = eccKey.LoadJwk(sbJwk.GetAsString)
If success = False Then
    Log(eccKey.LastErrorText)
    Return
End If


'  Create the JWS Protected Header
Dim jwsProtHdr As ChilkatJsonObject
jwsProtHdr.Initialize
jwsProtHdr.AppendString("alg", "ES256")

Dim jws As ChilkatJws
jws.Initialize

'  Set the protected header:
Dim signatureIndex As Int = 0
jws.SetProtectedHeader(signatureIndex, jwsProtHdr)

'  Set the ECC key:
jws.SetPrivateKey(signatureIndex, eccKey)

'  Set the payload.
Dim bIncludeBom As Boolean = False
Dim payloadStr As String = "In our village, folks say God crumbles up the old moon into stars."
jws.SetPayload(payloadStr, "utf-8", bIncludeBom)

'  Create the JWS
'  By default, the compact serialization is used.
Dim jwsCompact As String = jws.CreateJws
If jws.LastMethodSuccess = False Then
    Log(jws.LastErrorText)
    Return
End If


Log("JWS: " & jwsCompact)

'  Note: ECC signatures use random values, so the output will be different each time a signature is produced.
'  sample output:
'  JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

'  Now load the JWS, validate, and recover the original text.
Dim jws2 As ChilkatJws
jws2.Initialize

'  Load the JWS.
success = jws2.LoadJws(jwsCompact)

Dim eccPubKey As ChilkatPublicKey
eccPubKey.Initialize
eccKey.ToPublicKey(eccPubKey)

'  Set the ECC public key used for validation.
signatureIndex = 0
jws2.SetPublicKey(signatureIndex, eccPubKey)

'  Validate the 1st (and only) signature at index 0..
Dim v As Int = jws2.Validate(signatureIndex)
If v < 0 Then
    '  Perhaps Chilkat was not unlocked or the trial expired..
    Log("Method call failed for some other reason.")
    Log(jws2.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.")

'  Recover the original content:
Log(jws2.GetPayload("utf-8"))

'  Examine the protected header:
Dim joseHeader As ChilkatJsonObject
joseHeader.Initialize
jws2.GetProtectedH(signatureIndex, joseHeader)
joseHeader.EmitCompact = False

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

'  Output:

'  Signature validated.
'  In our village, folks say God crumbles up the old moon into stars.
'  Protected (JOSE) header:
'  { 
'    "alg": "ES256"
'  }