code review 6810051: go.crypto/bcrypt: add Cost function

go.crypto/bcrypt: add Cost function

Extracts the cost used to generate a bcrypt hash from the hash itself.

[jmhodges, 2012-10-30 07:05:30]

Hello agl@chromium.org (cc: dchest@gmail.com, golang-dev@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go.crypto

[agl1, 2012-10-30 16:37:38]

https://codereview.appspot.com/6810051/diff/1002/bcrypt/bcrypt.go
File bcrypt/bcrypt.go (right):

https://codereview.appspot.com/6810051/diff/1002/bcrypt/bcrypt.go#newcode117
bcrypt/bcrypt.go:117: // Cost returns the cost that the hashed password was made
with. This is
I don't think this comment is quite right. Why is Cost useful when a user's hash
needs to be made more difficult? (I know why, but not by reading the comment.)

// Cost returns the hashing cost used to create the given hashed password. When,
in the future, the hashing cost of a password system needs to be increased in
order to adjust for greater computational power, this function allows one to
establish which passwords need to be updated.

[dchest, 2012-10-30 16:49:59]

LGTM with agl's suggestion.

[jmhodges, 2012-10-30 16:56:42]

Hello agl@chromium.org, agl@golang.org, dchest@gmail.com (cc:
golang-dev@googlegroups.com),

Please take another look.

[jmhodges, 2012-10-31 16:31:47]

Gentlest of pings.

[agl1, 2012-10-31 16:36:10]

*** Submitted as
http://code.google.com/p/go/source/detail?r=7fd55a277056&repo=crypto ***

go.crypto/bcrypt: add Cost function

Extracts the cost used to generate a bcrypt hash from the hash itself.

R=agl, agl, dchest
CC=golang-dev
http://codereview.appspot.com/6810051

Committer: Adam Langley <agl@golang.org>