(Go) Create JWS Using Private Key on a Smart Card

See more JSON Web Signatures (JWS) Examples

Note: This example requires Chilkat v11.5.0 or greater.

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    success := false

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

    // Load the certificate from a smart card.
    cert := chilkat.NewCert()

    // Set the smarcard PIN prior to loading.
    cert.SetSmartCardPin("123456")

    // Detect the connected smartcard or USB security token and load the default certificate.
    success = cert.LoadFromSmartcard("")
    if success == false {
        fmt.Println(cert.LastErrorText())
        cert.DisposeCert()
        return
    }

    // Note: Chilkat provides many different ways to load a certificate from a smartcard or USB token,
    // such as selecting a certificate if the card contains multiple certificates with private keys,
    // or working with lower-level PKCS11 or ScMinidriver API's (both of which Chilkat provides).

    // Create the JWS Protected Header
    jwsProtHdr := chilkat.NewJsonObject()

    if cert.IsEcdsa() == true {
        jwsProtHdr.AppendString("alg","ES256")
    } else {
        jwsProtHdr.AppendString("alg","RS256")
    }

    jws := chilkat.NewJws()

    // Set the protected header:
    signatureIndex := 0
    jws.SetProtectedHeader(signatureIndex,jwsProtHdr)

    // Provide the private key via the certificate.
    // This requires Chilkat v11.5.0 or greater.
    jws.SetSigningCert(signatureIndex,cert)

    // Set the payload.
    bIncludeBom := false
    payloadStr := "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.
    jwsCompact := jws.CreateJws()
    if jws.LastMethodSuccess() == false {
        fmt.Println(jws.LastErrorText())
        cert.DisposeCert()
        jwsProtHdr.DisposeJsonObject()
        jws.DisposeJws()
        return
    }

    fmt.Println("JWS: ", *jwsCompact)

    // sample output:
    // JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

    // Now load the JWS, validate, and recover the original text.
    jws2 := chilkat.NewJws()

    // Load the JWS.
    success = jws2.LoadJws(*jwsCompact)

    pubKey := chilkat.NewPublicKey()
    cert.GetPublicKey(pubKey)

    // Set the public key used for validation.
    signatureIndex = 0
    jws2.SetPublicKey(signatureIndex,pubKey)

    // Validate the 1st (and only) signature at index 0..
    v := jws2.Validate(signatureIndex)
    if v < 0 {
        // Perhaps Chilkat was not unlocked or the trial expired..
        fmt.Println("Method call failed for some other reason.")
        fmt.Println(jws2.LastErrorText())
        cert.DisposeCert()
        jwsProtHdr.DisposeJsonObject()
        jws.DisposeJws()
        jws2.DisposeJws()
        pubKey.DisposePublicKey()
        return
    }

    if v == 0 {
        fmt.Println("Invalid signature.  The key was incorrect, the JWS was invalid, or both.")
        cert.DisposeCert()
        jwsProtHdr.DisposeJsonObject()
        jws.DisposeJws()
        jws2.DisposeJws()
        pubKey.DisposePublicKey()
        return
    }

    // If we get here, the signature was validated..
    fmt.Println("Signature validated.")

    // Recover the original content:
    fmt.Println(*jws2.GetPayload("utf-8"))

    // Examine the protected header:

    joseHeader := chilkat.NewJsonObject()
    success = jws2.GetProtectedH(signatureIndex,joseHeader)
    if success == false {
        fmt.Println(jws2.LastErrorText())
        cert.DisposeCert()
        jwsProtHdr.DisposeJsonObject()
        jws.DisposeJws()
        jws2.DisposeJws()
        pubKey.DisposePublicKey()
        joseHeader.DisposeJsonObject()
        return
    }

    joseHeader.SetEmitCompact(false)

    fmt.Println("Protected (JOSE) header:")
    fmt.Println(*joseHeader.Emit())

    // Output:

    // 	Signature validated.
    // 	In our village, folks say God crumbles up the old moon into stars.
    // 	Protected (JOSE) header:
    // 	{ 
    // 	  "alg": "RS256"
    // 	}

    cert.DisposeCert()
    jwsProtHdr.DisposeJsonObject()
    jws.DisposeJws()
    jws2.DisposeJws()
    pubKey.DisposePublicKey()
    joseHeader.DisposeJsonObject()