Verify Signature with public key P265r1

Question

I would like to verify a signature with a public key and can't find any way to do this in dart. In Swift, there is an easy solution via the SecKeyVerifySignature function. Is there something similar in flutter? I could only find the cryptography library but that won't let me set my own public key. Is there any way to archive this? Thanks in advance.

score 0 · Answer 1 · answered Jun 23 '21 at 14:32

0

Use the pointycastle package. ECDSASigner is initialized with an ECPublicKey..

  final verifier = ECDSASigner(SHA256Digest())
    ..init(
      false, // verify vs sign
      PublicKeyParameter(key), // key is an ECPublicKey
    );
  verifier.verifySignature(message, signature);

answered Jun 23 '21 at 14:32

Richard Heap

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Thanks. I have extracted my public key from a certificate via the ASN1Parser. So it is saved in a List. Is there a way to convert that list to an ECPublicKey? – Paul Jun 23 '21 at 14:50
Check out the `basic_utils` package and its method: `ECPublicKey ecPublicKeyFromDerBytes(Uint8List bytes);` – Richard Heap Jun 24 '21 at 00:16
It'll do the ASN.1 bits for you too, I think - check the `fromPem()` versions – Richard Heap Jun 24 '21 at 00:17
Did that help?? – Richard Heap Jun 25 '21 at 00:10
Some, there is a function called ```CryptoUtils.ecPublicKeyFromPem(String pem)```but it gives me the Error: ```_CastError (type 'ASN1Integer' is not a subtype of type 'ASN1ObjectIdentifier' in type cast)``` – Paul Jun 25 '21 at 17:16
It seems like the problem is the curve ```1.2.840.10045.4.3.2 ecdsaWithSHA256 (ANSI X9.62 ECDSA algorithm with SHA256)```. It isn't included in the package. Is there a way to implement that? – Paul Jun 25 '21 at 21:08
Are you able to update the question with the certificate PEM? – Richard Heap Jun 28 '21 at 16:30

Verify Signature with public key P265r1

1 Answers1