code review 3183043: crypto/cipher: add CFB and OCFB mode.

crypto/cipher: add CFB and OCFB mode.

        (Files which I left out of the initial commit to keep it small.)

[rsc, 2010-11-19 19:58:59]

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/cfb.go
File src/pkg/crypto/cipher/cfb.go (right):

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/cfb.go#...
src/pkg/crypto/cipher/cfb.go:19: func NewCFB(block Block, iv []byte, decrypt
bool) Stream {
I'd rather have NewCFBEncrypter and NewCFBDecrypter like the others.  Even if
they just call this (unexported) function internally, it's more consistent and
also avoids the "what does this bool mean?" problem when reading or writing
calls to NewCFB.

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/ocfb.go
File src/pkg/crypto/cipher/ocfb.go (right):

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/ocfb.go...
src/pkg/crypto/cipher/ocfb.go:16: // feedback mode using the given Block, and
the blockSize + 2 bytes of
It says "the blockSize + 2 bytes of ciphertext prefix"
but blockSize is not defined and more significantly
I don't understand what "the prefix" is.  Looks like it
has something to do with randData?

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/ocfb.go...
src/pkg/crypto/cipher/ocfb.go:45: // NewOCFBDecrypter returns a Stream which
decrypts data with OpenPGP's cipher
same

[agl1, 2010-11-19 20:32:53]

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/cfb.go
File src/pkg/crypto/cipher/cfb.go (right):

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/cfb.go#...
src/pkg/crypto/cipher/cfb.go:19: func NewCFB(block Block, iv []byte, decrypt
bool) Stream {
On 2010/11/19 19:58:59, rsc wrote:
> I'd rather have NewCFBEncrypter and NewCFBDecrypter like the others.  Even if
> they just call this (unexported) function internally, it's more consistent and
> also avoids the "what does this bool mean?" problem when reading or writing
> calls to NewCFB.

Done.

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/ocfb.go
File src/pkg/crypto/cipher/ocfb.go (right):

http://codereview.appspot.com/3183043/diff/2001/src/pkg/crypto/cipher/ocfb.go...
src/pkg/crypto/cipher/ocfb.go:16: // feedback mode using the given Block, and
the blockSize + 2 bytes of
On 2010/11/19 19:58:59, rsc wrote:
> It says "the blockSize + 2 bytes of ciphertext prefix"
> but blockSize is not defined and more significantly
> I don't understand what "the prefix" is.  Looks like it
> has something to do with randData?

I've taken out the comment about the size of the prefix and simply said that
it's initial amount of ciphertext. It's rather that case that, if you're using a
block cipher mode, you need to know its properties and the function comments are
only a guide to the knowledgeable.

[rsc1, 2010-11-19 20:52:55]

LGTM

[agl1, 2010-11-19 21:04:01]

Hello rsc (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[agl1, 2010-11-19 21:18:03]

*** Submitted as http://code.google.com/p/go/source/detail?r=45374ddea438 ***

	crypto/cipher: add CFB and OCFB mode.

        (Files which I left out of the initial commit to keep it small.)

R=rsc
CC=golang-dev
http://codereview.appspot.com/3183043

[agl1, 2010-11-19 21:18:22]

Submitted.