View Poll Results: Should we have a forum dedicated to Cryptography?

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  • Yes

    27 93.10%
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    2 6.90%
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Thread: Cryptography ( As posted by EtErNaL_L0ser)

  1. #16
    DakienDX
    Guest
    Hello everybody !

    Well, ok, start a new forum. If it's blessed by tsehp, it shoud become true. Here's my bless. (as if anyone woud care about that )

    Can someone correct the "\n" in the "Mini Project Area" 's forum description and the "with a 500k limit" in "Reverse Software Engineering General" 's forum description on the way to the new forum?
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  2. #17
    DakienDX
    Guest
    Hello ArthaXerXes !

    Thank you.

    It was nothing special, but it was anoying when looking at it every time going to the board.
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  3. #18
    tsehp
    Guest
    1- I'm not tired ;-) (artha likes to bite me here, because he's 10 years younger than me, but even ten years couldn't maybe corrupt a great amount of grey matter I built since those long and tiring rce years (3 in total,whaou !)

    A cryptology forum is badly needed, this feature is really not well covered on our archives and really deserves some comments,
    me thinks that we should directly start it without moderator at first, then we can naturally choose the guy that will participate the most.

    So it's just created, just tell me if the name deserves to be changed.

    LONG LIFE TO THE Rce cryptographics !!!
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  4. #19
    DakienDX
    Guest
    Hello tsehp !

    LONG LIFE TO THE Rce cryptographics !!!

    You should now change all forum descriptions to "flames, crack, serial and bruteforce requests will be removed"
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  5. #20
    EtErNaL_L0ser
    Guest

    heheh

    Yeah no lame post! But some resources
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  6. #21
    McCodEMaN
    Guest

    Talking GREAT!!

    Greetings everyone!

    I'm glad to see that a forum finally was created for such a important and thrilling subject, as I belive that this is!
    I hope to see many interesting posts in the future , and perhaps even share some of my ideas.

    Regards
    McCodEMaN
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  7. #22
    הבּרוּ נשׂאי כּלי יהוה mike's Avatar
    Join Date
    Mar 2001
    Posts
    491
    Originally posted by DakienDX
    ...
    I think no one can explain why RSA works or why SHA was converted to SHA-1.
    ...
    I can do both.

    First is Fermat's Little Theorem:

    a^(p-1) mod p = 1, where p is prime, ^ is exponentiation, and a is any number less than p. So

    a^b mod p = a^(b mod p-1) mod p.

    That implies that for n=p1 * p2 * ... * pk, the product of kdistinct primes, that a^(p1-1)(p2-1)...(pk-1) = 1. This product in the exponent is usually called phi(n).

    So a^b mod n = a^(b mod phi(n)) mod n.

    So pick two large primes p and q, and multiply them to get n. Then phi(n) = (p-1)(q-1).

    Now, you want a two step process, encrypt then decrypt, so that you get the same number back. Well, a^1=a, obviously, so you need two exponents whose product equals 1 mod phi(n).

    Pick e at random, and since you know phi(n), you can calculate

    d = e^-1 mod n

    Publish n and e as your public key. In order to break the code, you need to find d. You could calculate it if you knew (p-1)(q-1), but the only way anyone knows how to get that from n is to factor it. This is very hard.

    Then to encrypt your message M, you have

    C=M^e mod n

    and to decrypt you have

    C^d mod n = M^ed mod n = M^(ed mod phi(n)) mod n
    = M^1 mod n = M.

    Voila!

    SHA was probably changed to SHA-1 to avoid an attack that works somewhat like differential cryptanalysis. I say probably because a guy later found an attack that works on SHA-0 but not on SHA-1. If anyone is interested, I can post the reference.
    Last edited by mike; October 22nd, 2002 at 02:45.

  8. #23
    EtErNaL_L0ser
    Guest

    Talking eehehhehe

    Leonhard Euler and Pierre de Fermat both prime-number guys! They got great theorems

    One mus know them all!
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  9. #24
    Sphinx
    Guest

    Thumbs up

    hello you all

    well i would say get this topic of the ground, i`m very in too this
    i sure want to learn more on this. I have been searching on the web and collection info but as said before you have to have a background to fall back on becuz it`s very very hard. The math involved ain`t easy.

    also rv it is difficult becuz lot of cyphers work on the idea big key so hard to brute force. It takes time sometimes lots of it. math is involved to calc the time needed to crypt and decrypt it.


    i`m checking this thread often now

    Sphinx
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  10. #25
    Sphinx
    Guest

    Question

    maybe you can look here h**p://www.claymath.org/prizeproblems/index.htm
    these are some big math problems unsolved (yes you can win money) but my point is some off these problems are used in cryptography cuz No one is yet able to use a function to get to an answer in stead you`ll have to go by all possibilties takes time a lot of time just think of prime numbers we can generate them but we can`t say

    function p(x) = prime (p is a function not yet discoverd)
    say i want the 100th prime number fill in x=100 and you get your 100th prime number

    the p versus np problem is something like that too
    I promise that I have read the FAQ and tried to use the Search to answer my question.

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