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

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) using the private key associated with a certificate on a smart card.

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

    // 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()
    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).

    // If the associated private key was present on the smartcard, then you can simply
    // get it from the Chilkat cert object:
    privKey := cert.ExportPrivateKey()
    if cert.LastMethodSuccess() == false {
        fmt.Println(cert.LastErrorText())
        cert.DisposeCert()
        return
    }

    // You can check the key type to make sure it's RSA.
    // This will output "rsa" if the key is RSA.
    fmt.Println("Key type = ", privKey.KeyType())

    // Create the JWS Protected Header
    jwsProtHdr := chilkat.NewJsonObject()
    jwsProtHdr.AppendString("alg","RS256")

    jws := chilkat.NewJws()

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

    // Set the RSA key:
    jws.SetPrivateKey(signatureIndex,privKey)

    // 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() != true {
        fmt.Println(jws.LastErrorText())
        privKey.DisposePrivateKey()
        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)

    rsaPubKey := privKey.GetPublicKey()
    privKey.DisposePrivateKey()

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

    // 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()
        return
    }

    if v == 0 {
        fmt.Println("Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both.")
        cert.DisposeCert()
        jwsProtHdr.DisposeJsonObject()
        jws.DisposeJws()
        jws2.DisposeJws()
        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 := jws2.GetProtectedHeader(signatureIndex)
    if jws2.LastMethodSuccess() != true {
        fmt.Println("No protected header found at the given index.")
        cert.DisposeCert()
        jwsProtHdr.DisposeJsonObject()
        jws.DisposeJws()
        jws2.DisposeJws()
        return
    }

    joseHeader.SetEmitCompact(false)

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

    // 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()