Talk:Main step of GOST 28147-89

task specifics

Hi,

• What is goal of the task?
• How does one know one has completed the task?
• Do you have sample tests and sample output?

- Thanks. --Paddy3118 20:22, 31 August 2012 (UTC)

Hi!

• The goal of the task is the comparison of programming languages for the implementation of some specific cryptographic algorithm, originally designed for efficient execution on 32-bit and 64-bit machines (though created in the 70's), while it operates with a 4-bit block; comparison of low-level with high-level languages in this aspect for the sake of brevity and clarity of code execution speed, consumption of computer resources and so on.
• The task can be considered solved if the algorithm is implemented only true converts the input data.
• Verification example can be used as follows:

the input is a text block size of 8 bytes:

[21][04][3B][04][30][04][32][04];

and item key, size 4 bytes:

[F9][04][C1][E2].

Incoming text block is divided into two parts:

[21][04][3B][04] и [30][04][32][04].

First we add modulo 2³² with the received key element, the result is

[1A][09][FC][E6].

Further, in this block is replaced with the replacement table. Are replaced by:

[A] to [1], [1] to [B], [9] to [F], [0] to [7], [C] to [0], [F] to [E], [6] to [5] and [E] to [8].

Finally, we obtain

[B1][7F][E0][85].

Next is the cyclic shift of reading towards senior level by 11 bits:

[2F][8C][FD][03].

This value is made up bit by bit modulo 2 with the second part on the input 8-bit block, the result is

[1F][88][CF][07].

Now is 8-byte block of data in the first part of which is located just obtained value, and the second - the first part was on the input 8-byte block. The resulting value

[1F][88][CF][07][21][04][3B][04]

and will be the result of the step.

Русский 18:54, 1 September 2012 (UTC)

Is there a definitive link to the definition of the algorithm? It sounds like it's something controlled by an external body, so a definitive link (or reference to paper version, of course) ought to be possible. (If the link is to an English-language version, so much the better, but being definitive is better than being readable to me.) I ask because while I could implement the task by copying an existing solution (the C version looks easy enough to copy), I would have no idea at all whether all I'd be doing is copying their mistakes! I love to be able to independently check the correctness of any code I write. –Donal Fellows 10:10, 7 September 2012 (UTC)

Yes, of course, a reference to the text of the standard, some of which I have implemented the proposed algorithm for the job, I have: [1]. This is a scanned version of the paper edition of the standard. But, unfortunately, I have it is only in Russian, but in the annexes have a pretty clear flowchart. Here is a diagram of the basic step: [2]. Русский 13:13, 8 September 2012 (UTC)

As you can see, I have given a description of two embodiments of the algorithm: the classical and variant with a compressed table changes. The latter has traditionally been used in implementations on low-level languages, and the first is more beautiful and obvious, therefore, in my opinion, it is better to start with him (option for "JavaScript"). Русский 13:17, 8 September 2012 (UTC)