Results 1 to 6 of 6

Thread: RSA/DSA problem calculating X^(-1)

  1. #1
    DakienDX
    Guest

    RSA/DSA problem calculating X^(-1)

    Hello everybody !

    Can someone please help me. Both RSA and DSA use an calculation in the form of X^(-1), where X is an integer and the result is an integer too.

    But as far as I know, X^(-1) is the same as 1/(X^1) and the result is a real and not an integer.

    ex. 2^(-2) = 1/(2^2) = 0.25
    ex. 10^(-1) = 1/(10^1) = 0.1

    Thank you for any help.
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  2. #2
    goatass
    Guest
    Hi there, from what I learned on RSA, they do not use integers they use BIG number which is a data type especially for the use of large number.
    I don't know what calculations you are talking about exactly, there are millions of things you can do with RSA/DSA.

    I guess what I'm asking is for you to give some more info on what calculation you are trying to achieve and for what.

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

  3. #3
    DakienDX
    Guest
    Hello goatass !

    To be more specified, in RSA, the private exponent D is calculated D=E^(-1) mod ((P-1)*(Q-1)).

    In DSA it's S=(K^(-1)*(SHA(M)+X*R) mod Q and W=S^(-1) mod Q.

    I know that a "BigNum" is a kind of integer, at least it is no real data type.

    The D from RSA can be calculated by using some tools (like RSA-Tool 2 by tE!), but in DSA you have to do those calculations everytime you want to sign a message or verify it.
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  4. #4
    Spath.
    Guest
    Read again the definitions, RSA and DSA are
    based on *modular* arithmetics, therefore
    modular inverses are always integers. In short,
    r is the inverse of m modulo n if there exist a
    integer k such that k.n + 1 = m.r, which you
    can solve (when possible) with for instance
    the extended euclidean algorithm.
    I promise that I have read the FAQ and tried to use the Search to answer my question.

  5. #5
    AdamA
    Guest
    Hi,
    look at http://indigo.ie/~mscott/
    There are some DSA/RSA examples in this lib.

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

  6. #6
    DakienDX
    Guest
    Hello everybody !

    Thank you all for your help!
    I promise that I have read the FAQ and tried to use the Search to answer my question.

Similar Threads

  1. Typelibrary calculating function offset
    By Iwarez in forum Malware Analysis and Unpacking Forum
    Replies: 0
    Last Post: June 7th, 2002, 18:53
  2. Thanks +Tsehp, problem solve Isp problem :)
    By esther in forum Advanced Reversing and Programming
    Replies: 1
    Last Post: October 28th, 2000, 07:29

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •