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// Copyright 2019 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package signature_test
// [START signature-example]
import (
"bytes"
"fmt"
"log"
"github.com/tink-crypto/tink-go/v2/insecurecleartextkeyset"
"github.com/tink-crypto/tink-go/v2/keyset"
"github.com/tink-crypto/tink-go/v2/signature"
)
func Example() {
// A private keyset created with
// "tinkey create-keyset --key-template=ECDSA_P256 --out private_keyset.cfg".
// Note that this keyset has the secret key information in cleartext.
privateJSONKeyset := `{
"key": [{
"keyData": {
"keyMaterialType":
"ASYMMETRIC_PRIVATE",
"typeUrl":
"type.googleapis.com/google.crypto.tink.EcdsaPrivateKey",
"value":
"EkwSBggDEAIYAhogEiSZ9u2nDtvZuDgWgGsVTIZ5/V08N4ycUspTX0RYRrkiIHpEwHxQd1bImkyMvV2bqtUbgMh5uPSTdnUEGrPXdt56GiEA3iUi+CRN71qy0fOCK66xAW/IvFyjOGtxjppRhSFUneo="
},
"keyId": 611814836,
"outputPrefixType": "TINK",
"status": "ENABLED"
}],
"primaryKeyId": 611814836
}`
// The corresponding public keyset created with
// "tinkey create-public-keyset --in private_keyset.cfg"
publicJSONKeyset := `{
"key": [{
"keyData": {
"keyMaterialType":
"ASYMMETRIC_PUBLIC",
"typeUrl":
"type.googleapis.com/google.crypto.tink.EcdsaPublicKey",
"value":
"EgYIAxACGAIaIBIkmfbtpw7b2bg4FoBrFUyGef1dPDeMnFLKU19EWEa5IiB6RMB8UHdWyJpMjL1dm6rVG4DIebj0k3Z1BBqz13beeg=="
},
"keyId": 611814836,
"outputPrefixType": "TINK",
"status": "ENABLED"
}],
"primaryKeyId": 611814836
}`
// Create a keyset handle from the cleartext private keyset in the previous
// step. The keyset handle provides abstract access to the underlying keyset to
// limit the access of the raw key material. WARNING: In practice,
// it is unlikely you will want to use a insecurecleartextkeyset, as it implies
// that your key material is passed in cleartext, which is a security risk.
// Consider encrypting it with a remote key in Cloud KMS, AWS KMS or HashiCorp Vault.
// See https://github.com/google/tink/blob/master/docs/GOLANG-HOWTO.md#storing-and-loading-existing-keysets.
privateKeysetHandle, err := insecurecleartextkeyset.Read(
keyset.NewJSONReader(bytes.NewBufferString(privateJSONKeyset)))
if err != nil {
log.Fatal(err)
}
// Retrieve the Signer primitive from privateKeysetHandle.
signer, err := signature.NewSigner(privateKeysetHandle)
if err != nil {
log.Fatal(err)
}
// Use the primitive to sign a message. In this case, the primary key of the
// keyset will be used (which is also the only key in this example).
data := []byte("data")
sig, err := signer.Sign(data)
if err != nil {
log.Fatal(err)
}
// Create a keyset handle from the keyset containing the public key. Because the
// public keyset does not contain any secrets, we can use [keyset.ReadWithNoSecrets].
publicKeysetHandle, err := keyset.ReadWithNoSecrets(
keyset.NewJSONReader(bytes.NewBufferString(publicJSONKeyset)))
if err != nil {
log.Fatal(err)
}
// Retrieve the Verifier primitive from publicKeysetHandle.
verifier, err := signature.NewVerifier(publicKeysetHandle)
if err != nil {
log.Fatal(err)
}
if err = verifier.Verify(sig, data); err != nil {
log.Fatal(err)
}
fmt.Printf("sig is valid")
// Output: sig is valid
}
// [END signature-example]
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