Visual FoxPro

Sign a JWS with an HMAC Key

See more JSON Web Signatures (JWS) Examples

Demonstrates Jws.SetMacKey, which sets the symmetric MAC key for a signature. The key bytes are supplied in a named encoding such as hex or base64.

Background. HMAC-based JWS (for example HS256) authenticates the payload with a shared symmetric key that both signer and verifier possess.

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LOCAL lnSuccess
LOCAL loJws
LOCAL loHeader
LOCAL lnBIncludeBom
LOCAL lcBase64Key
LOCAL lcJwsCompact

lnSuccess = 0

loJws = CreateObject('Chilkat.Jws')

*  Protected header specifying HMAC-SHA256.
loHeader = CreateObject('Chilkat.JsonObject')
loHeader.UpdateString("alg","HS256")
lnSuccess = loJws.SetProtectedHeader(0,loHeader)
IF (lnSuccess = 0) THEN
    ? loJws.LastErrorText
    RELEASE loJws
    RELEASE loHeader
    CANCEL
ENDIF

lnBIncludeBom = 0
lnSuccess = loJws.SetPayload("This is the content to sign.","utf-8",lnBIncludeBom)
IF (lnSuccess = 0) THEN
    ? loJws.LastErrorText
    RELEASE loJws
    RELEASE loHeader
    CANCEL
ENDIF

*  Set the symmetric MAC key for signature 0.  The key bytes are provided in the named encoding (here
*  base64).  In production, obtain the key from a secure source rather than hard-coding it.
lcBase64Key = "YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXowMTIzNDU="
lnSuccess = loJws.SetMacKey(0,lcBase64Key,"base64")
IF (lnSuccess = 0) THEN
    ? loJws.LastErrorText
    RELEASE loJws
    RELEASE loHeader
    CANCEL
ENDIF

lcJwsCompact = loJws.CreateJws()
IF (loJws.LastMethodSuccess = 0) THEN
    ? loJws.LastErrorText
    RELEASE loJws
    RELEASE loHeader
    CANCEL
ENDIF

? lcJwsCompact

RELEASE loJws
RELEASE loHeader