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package cose_test
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"fmt"
"github.com/veraison/go-cose"
)
// This example demonstrates signing and verifying COSE_Sign1 signatures.
func ExampleCWTMessage() {
// create message to be signed
msgToSign := cose.NewSign1Message()
msgToSign.Payload = []byte("hello world")
msgToSign.Headers.Protected.SetAlgorithm(cose.AlgorithmES512)
msgToSign.Headers.Protected.SetType("application/cwt")
claims := cose.CWTClaims{
cose.CWTClaimIssuer: "issuer.example",
cose.CWTClaimSubject: "subject.example",
}
msgToSign.Headers.Protected.SetCWTClaims(claims)
msgToSign.Headers.Unprotected[cose.HeaderLabelKeyID] = []byte("1")
// create a signer
privateKey, err := ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
if err != nil {
panic(err)
}
signer, err := cose.NewSigner(cose.AlgorithmES512, privateKey)
if err != nil {
panic(err)
}
// sign message
err = msgToSign.Sign(rand.Reader, nil, signer)
if err != nil {
panic(err)
}
sig, err := msgToSign.MarshalCBOR()
// uncomment to review EDN
// coseSign1Diagnostic, err := cbor.Diagnose(sig)
// fmt.Println(coseSign1Diagnostic)
if err != nil {
panic(err)
}
fmt.Println("message signed")
// create a verifier from a trusted public key
publicKey := privateKey.Public()
verifier, err := cose.NewVerifier(cose.AlgorithmES512, publicKey)
if err != nil {
panic(err)
}
// verify message
var msgToVerify cose.Sign1Message
err = msgToVerify.UnmarshalCBOR(sig)
if err != nil {
panic(err)
}
err = msgToVerify.Verify(nil, verifier)
if err != nil {
panic(err)
}
fmt.Println("message verified")
// tamper the message and verification should fail
msgToVerify.Payload = []byte("foobar")
err = msgToVerify.Verify(nil, verifier)
if err != cose.ErrVerification {
panic(err)
}
fmt.Println("verification error as expected")
// Output:
// message signed
// message verified
// verification error as expected
}
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