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bitRAKE



Joined: 21 Jul 2003
Posts: 2937
Location: vpcmipstrm
bitRAKE
XMM0 is ambiguous beyond DQWORD - only in use does it become further defined. Because the instruction set is not constant the union of all uses of XMM0 also changes (although, I doubt it will). From a programming point of view much more is gained by typing in agreement with the instruction, and it seems logical to me. If that were the case then the MOV* instructions would still require DQWORD as their type. (Just talking about SSE*.)

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Post 23 Aug 2008, 14:51
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lazer1



Joined: 24 Jan 2006
Posts: 185
lazer1
it is useful to at least have a define dqword 0, where all bits are 0.

that is useful for:

struc xmm_values
{
.xmm0 do 0
.xmm1 do 0
....
.xmm15 do 0
.mm0 dq 0
}

virtual at 0
xmm_values xmm_values
end virtual

movupd [ rax + xmm_values.xmm0 ], xmm0
movupd [ rax + xmm_values.xmm1 ], xmm1
....

here the type is 128 UNINTERPRETED bits,

ie multi-type,

and eg the following is an ERROR:
movupd [ rax + xmm_values.mm0 ], xmm0 ; WRONG!

because the dest operand has type 64 uninterpreted bits.

movupd dqword [ rax + xmm_values.mm0 ], xmm0 ; CORRECT!
Post 23 Aug 2008, 18:06
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lazer1



Joined: 24 Jan 2006
Posts: 185
lazer1
revolution wrote:
PGP is not banned in the US. Where do you get that idea?


the guy who created it got into trouble, I think for use in the USA
it needs a backdoor for the CIA.

excerpt from PGP:

Quote:

Pretty Good Privacy version 2.6.3/2.6.3i - READ ME FIRST

1996/01/18


The PGP 2.6.3i source code tree is able to compile both the international
version of PGP (PGP 2.6.3i) and the USA version of PGP (PGP 2.6.3). It
includes the source code for Unix, MS-DOS, AmigaDOS, MacOS, VMS, and other
systems.


INTERNATIONAL VERSION -- PGP 2.6.3i
- -----------------------------------

Users outside the USA should use the international version of PGP, the
latest version of which is PGP 2.6.3i.

--> For more information, read the file "readme.1st".


USA VERSION -- PGP 2.6.3
- ------------------------

Users inside the USA, because of patent laws, should use PGP 2.6.3, which
uses the RSAREF library. This version is completely legal to use for non-
commercial purposes inside the USA. It is not an official MIT release of
PGP; rather, it is based on the latest official MIT release (PGP 2.6.2)
together with the enhancements which are also in PGP 2.6.3i.



according to that PGP 2.6.3i cannot be used in the US although
the reason given above is patent laws.



Quote:

I think you are actually talking about the RSA scheme, PGP uses RSA for key distribution, but not for direct message encryption.


I am not an expert on this!

I think in the US you arent allowed to use encryption unless
the CIA (or is it FBI) can listen in. You probably need to
supply the key encrypted via a CIA key. That way the CIA
can always listen in but others cannot.

but you could always get around that by storing an encrypted message
in the lower bits of an audio file!


Quote:

128 bit integers are not nearly big enough for the RSA based encryption schemes if one wants a secure system. You will still need to use multiple 128 bit registers to make a larger sized modulus.


according to the PGP key generator:

512 bits : low commercial grade,
768 bits : high commercial grade
1024 bits : military grade

I use 1030 bits!

it takes a bit of time to encrypt a 2mb compressed archive.

Quote:

I would think that using PGP to encrypt all your data is not the best way to secure your own documents.


the idea is to unencrypt, work on the unencrytped version and then
right at the end re-encrypt and permanently erase the unencrypted version
eg by doing a full reformat of a small temporary volume.

amongst other things this methodology forces you to have plenty
of backups,


Quote:

Better would be one of the much simpler, easier and faster symmetric cyphers.


what is the principle of those?

Quote:

This also allows you to keep a password in your head. Using RSA style encryptions requires a large secret key to be secured also.


that is a disadvantage for military use as the enemy can capture a soldier
and find the key by torture. Twisted Evil

(we have ways of making you talk!)

with PGP as long as the soldier destroys the private key they cannot
find it by torture. Razz

keep the key on a special USB drive which self destructs if you press
a button! Confused

Quote:

Also, taking vid's comment out of context is not being fair. vid was talking about the assembly code aspect of a dqword operator, not the data contained within a 128 bit register.


I was quoting it the way I understood it which could be different from
what he meant!

everyone interprets the same text differently, I genuinely interpreted
what he said the way I quoted it.

for most uses anyway you dont need more than 64 bits, its just for
very specialised situations where you need that, often you just
need 32 bits. But to deal with a 120G drive you need to go beyond
32 bit.

and a DVD is a bit more than 32 bits, 4.7G according to the label.
Post 23 Aug 2008, 19:30
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
Quote:
for most uses anyway you dont need more than 64 bits, its just for very specialised situations where you need that, often you just
need 32 bits. But to deal with a 120G drive you need to go beyond
32 bit.

How about pointers on x64 machine - not a "common case"?
Post 23 Aug 2008, 19:36
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17467
Location: In your JS exploiting you and your system
revolution
lazer1: Your information is so old now that it has become inaccurate. PGP is NOT banned in the US (and has never been banned in the US) for any purpose. It was once, in the distant past, banned from EXPORT out of the US, that was all, but that restriction was lifted about 10 years ago. There is no requirement for a backdoor either.

If you are concerned about being tortured to get your key then I suggest you don't use any encryption. How is your life worth more than the data you have?
Post 23 Aug 2008, 19:37
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17467
Location: In your JS exploiting you and your system
revolution
lazer1: have a look at truecrypt (google it), it probably does just what you need.
Post 23 Aug 2008, 19:39
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MCD



Joined: 21 Aug 2004
Posts: 604
Location: Germany
MCD
lazer1: also, using 1030 bit key instead of 1024 bit is a joke. Either 1024bit is enough for you, or you should use 1536bits, 2048bits...
Post 24 Aug 2008, 05:12
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
Quote:
it takes a bit of time to encrypt a 2mb compressed archive.

That's why sane people use RSA only to encrypt AES key, and then encrypt actual big data with AES/EAX, or something like that.
Post 24 Aug 2008, 07:53
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