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Date: Thu, 12 Apr 2012 16:51:40 -0500
From: "jfoug" <jfoug@....net>
To: <john-dev@...ts.openwall.com>
Subject: RE: PDF format
Almost all of the speed problems, within the salt system, are calling crack
to test for 'something', when you do not have a password. IF (and that's a
big if), this code really does need to be done, then we should ONLY do this
at load time, and not every time we reload a salt.
if (encdata->revision == 2) {
if (knownPassword) {
if (!isUserPasswordRev2())
return false;
memcpy(encKeyWorkSpace, pad, 32);
} else {
memcpy(password_user, pad, 32);
** //knownPassword = isUserPasswordRev2();
++ knownPassword = true;
}
} else if (e->revision >= 3) {
memcpy(buf, pad, 32);
memcpy(buf + 32, e->fileID, e->fileIDLen);
tmp = malloc(sizeof(uint8_t) * 16);
md5(buf, 32 + e->fileIDLen, tmp);
rev3TestKey = tmp;
if (knownPassword) {
if (!isUserPasswordRev3())
return false;
memcpy(encKeyWorkSpace, pad, 32);
} else {
memcpy(password_user, pad, 32);
** //knownPassword = isUserPasswordRev3();
++ knownPassword = true;
}
I show where I simply comment things out ( the ** lines ), and where I added
new lines ( the ++ lines ). I am not sure the ++ is correct or not. By
making only these changes (and those functions are the workhorses called
within the crypt_all function), then multi-salt runs at 95% the speed of 1
salt (vs about 45% in the current build).
Jim.
>-----Original Message-----
>From: Dhiru Kholia [mailto:dhiru.kholia@...il.com]
>Sent: Thursday, April 12, 2012 10:17 AM
>To: john-dev@...ts.openwall.com
>Subject: Re: [john-dev] PDF format
>
>On Sun, Mar 25, 2012 at 6:47 PM, <jfoug@....net> wrote:
>> The logic in get_salt() and set_salt() should be reversed.
>>
>> Within pdf (and a few other formats), a lot of time is spent within
>the set_salt function, parsing, allocating, setting up a complex
>structure. This type of work should NOT be done within the runtime
>loop. If done in set_key(), then it is in the runtime loop, and each
>salt computation will be done for EACH salt for EACH password (block of
>pw's) attempted. This time spent in set_salt() will GREATLY slow down
>the format.
>> If this same logic is moved to get_salt(), then it will be done ONE
>time, for each salt, at the load time of john. There will be no runtime
>penalty for a 'complex' salt.
>
>This is now done and committed to magnum-jumbo. However "many salts"
>case is still slower than "one salt" case. Is this due to initPDFCrack
>function being called from set_salt?
>
>--
>Cheers,
>Dhiru
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