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Date: Sat, 29 Dec 2012 00:24:44 +0100
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: Formats dmg, encfs and strip crash on longer passwords

On 28 Dec, 2012, at 19:17 , Frank Dittrich <frank_dittrich@...mail.com> wrote:
> On 12/28/2012 06:21 PM, Dhiru Kholia wrote:
>> What should be the max password length (which actually works) for
>> formats using your pbkdf2 code?. Can it be increased?

I believe Lukas' limit is 16. I increased it for my GPU code (current git version of wpapsk-opencl and krb5pa-sha1-opencl) because the imposed limit made no gain and I hate limiting our supported lengths for no reason. There might be valid reasons to do it in the CPU code, I'm not sure (but I can't think of any). My limits are dictated by SHA1 block sizes: max salt length 52 and max plaintext length 64.

> The more interesting question is: what is the maximum password length
> supported by the software which creates/uses these hashes?
> 
> Then we can decide how to adjust these formats:
> -Mac OS X Keychain PBKDF2-HMAC-SHA-1 3DES
> -Apple DMG PBKDF2-HMAC-SHA-1 3DES / AES
> -STRIP Password Manager PBKDF2-SHA1
> -EncFS PBKDF2 AES / Blowfish
> -1Password Agile Keychain PBKDF2-HMAC-SHA-1 AES
> -Kerberos 5 AS-REQ Pre-Auth etype 17/18 aes-cts-hmac-sha1-96
> 
> For some reason, I didn't find a problem with max. password length for
> krb5pa-sha1, even though it claims to support passwords with a length of
> up to 125 bytes.

The krb5pa-sha1 CPU format use Lukas code up to length 16 but switches to Gladman code for longer keys (isn't OpenSSL better than the latter by the way?). So that format supports lengths up to 125 but with better speed at 16 or shorter. Maybe some or all of the other formats can do the same?

magnum

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