Crypto: use a rich object to represent a message digest (instead of list of bytes)

[DartBot]

Originally opened as dart-lang/sdk#2875

This issue was originally filed by [email protected]

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In its current shape, the hash and HMAC functions in the crypto library return List<int> as a message digest. This has several deficiencies:

1. If you want to print it, you need an extra function to convert it to string (see issue #2839).
2. If you want to compare it and use the hashes for passwords, you have to be very careful to avoid timing attacks (se http://codahale.com/a-lesson-in-timing-attacks/).

Therefore, I propose to use a rich object called Digest instead. It would look like this:

interface Digest {
  final List<int> bytes;

  // TODO operator equals, when implemented
  bool operator ==(Digest other);

  String toString();
}

I'm attaching a patch with complete implementation (necessary modifications to tests included). Note that if you accept this, it supersedes issue #2839.

Please note that I DON'T really understand crypto, so if you decide to accept this API change, proper crypto review is a good idea :-)

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Attachment:
0001-represent-message-digest-as-a-rich-object-with-bette.patch (9.72 KB)

[DartBot]

Comment by madsager

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Added Area-Library, Triaged labels.

[DartBot]

Comment by ladicek

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This comment was originally written by [email protected]

To increase likelihood of getting this applied (or at least considered), I'm attaching a new version of the patch that applies cleanly to current Dart tree.

I intentionally didn't remove the CryptoUtils.bytesToHex function, because it might be useful for other stuff too, not only for digests.

Attachment:
0001-represent-message-digest-as-a-rich-object-with-bette.patch (10.87 KB)

[sethladd]

Dupe of #177