code review 5307060: crypto/rsa: change public exponent from 3 to 65537

crypto/rsa: change public exponent from 3 to 65537

Although there's still no concrete security reason not to use 3, I
think Bleichenbacher has convinced me that it's a useful defense and
it's what everyone else does.

[agl1, 2011-10-26 14:09:22]

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

I'd like you to review this change to
https://go.googlecode.com/hg/

[rsc, 2011-10-26 14:30:50]

LGTM

[bradfitz, 2011-10-26 14:34:21]

LGTM

On Wed, Oct 26, 2011 at 7:09 AM, <agl@golang.org> wrote:

> Reviewers: bradfitz,
>
> Message:
> Hello bradfitz@golang.org (cc: golang-dev@googlegroups.com),
>
> I'd like you to review this change to
> https://go.googlecode.com/hg/
>
>
> Description:
> crypto/rsa: change public exponent from 3 to 65537
>
> Although there's still no concrete security reason not to use 3, I
> think Bleichenbacher has convinced me that it's a useful defense and
> it's what everyone else does.
>
> Please review this at
http://codereview.appspot.com/**5307060/<http://codereview.appspot.com/5307060/>
>
> Affected files:
>  M src/pkg/crypto/rsa/rsa.go
>
>
> Index: src/pkg/crypto/rsa/rsa.go
> ==============================**==============================**=======
> --- a/src/pkg/crypto/rsa/rsa.go
> +++ b/src/pkg/crypto/rsa/rsa.go
> @@ -116,15 +116,7 @@
>  // [2] http://www.cacr.math.**uwaterloo.ca/techreports/2006/**
>
cacr2006-16.pdf<http://www.cacr.math.uwaterloo.ca/techreports/2006/cacr2006-16.pdf>
>  func GenerateMultiPrimeKey(random io.Reader, nprimes int, bits int) (priv
> *PrivateKey, err os.Error) {
>        priv = new(PrivateKey)
> -       // Smaller public exponents lead to faster public key
> -       // operations. Since the exponent must be coprime to
> -       // (p-1)(q-1), the smallest possible value is 3. Some have
> -       // suggested that a larger exponent (often 2**16+1) be used
> -       // since previous implementation bugs[1] were avoided when this
> -       // was the case. However, there are no current reasons not to use
> -       // small exponents.
> -       // [1]
http://marc.info/?l=**cryptography&m=**115694833312008&w=2<http://marc.info/?...
> -       priv.E = 3
> +       priv.E = 65537
>
>        if nprimes < 2 {
>                return nil, os.NewError("rsa.**GenerateMultiPrimeKey:
> nprimes must be >= 2")
>
>
>

[agl1, 2011-10-26 14:41:57]

*** Submitted as http://code.google.com/p/go/source/detail?r=3fe4f3f34e9b ***

crypto/rsa: change public exponent from 3 to 65537

Although there's still no concrete security reason not to use 3, I
think Bleichenbacher has convinced me that it's a useful defense and
it's what everyone else does.

R=bradfitz, rsc
CC=golang-dev
http://codereview.appspot.com/5307060