Re: WebCrypto AlgorithmIdentifier for ECDSA signing w/SECP256R1 & SHA-256 ?

On Wed, Dec 16, 2015 at 5:02 PM, Hodges, Jeff <jeff.hodges@paypal.com>
wrote:

> Hi,
>
> how does one specify a WebCrypto AlgorithmIdentifier such that it
> represents "sign operation using ECDSA key on SECP256R1 curve with SHA-256
> hash" ?
>
> Here's my guess:
>
>   // WebCrytpo AlgorithmIdentifier stipulating:
>   //
>   //  "sign operation using ECDSA key on SECP256R1 curve with SHA-256 hash"
>   //
>   // See: http://www.w3.org/TR/WebCryptoAPI/#ecdsa
>   //
>   // Note: the private key used to sign MUST have been created using
>   //       NIST recommended curve P-256, also known as secp256r1, and with
>   //       a KeyUsage including "sign".
>   //
>
>   var algSign__ECDSA_SECP256R1_SHA256 = {
>     name: "ECDSA",
>     hash: "SHA-256"
>   }
>
> Is that correct, including the "Note:" in the comment ?
>

var data = ...;
return window.crypto.subtle.generateKey({ "name": "ECDSA", "namedCurve":
"P-384"}, false, ["sign", "verify"]).then(keyPair => {
  return window.crypto.subtle.sign({ "name": "ECDSA", "hash": { "name":
"SHA-256" } }, keyPair.privateKey, data).then(signature => {
    return window.crypto.subtle.verify({ "name": "ECDSA", "hash":
"SHA-256"}, keyPair.publicKey, signature, data).then(verified => {
      if (verified) {
        return { "data": data, "signature": signature };
      } else {
        return null;
      }
  });
});

Will return a promise that either resolves to an object with the data and
signature - if it can generate a key that can sign and then verify the data
- or null if it can't.

Two different forms of Hash are used as two different forms are acceptable
for AlgorithmIdentifier.