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Calculating Euler phi function

  1. Nov 18, 2008 #1
    How do i comput the euler phi function of a large interger?
    i know that if p is prime then phi(p)=p-1 and i've found a formula for computing non primes but i dont know how to implement in something like Matlab.
    Does anyone know how?
  2. jcsd
  3. Nov 19, 2008 #2
    AFAIK, computing the Euler phi function requires you to know the prime factorization of the input. Unless you can find it, there's not much you can do.
  4. Nov 25, 2008 #3
    Yes i know the factorisation problem is hard. Im workin with RSA encryption so we know two large primes, the product of which is N this is what i want to do euler phi on.
    Since N is the product of two primes (p and q) is phi(N) simply (p-1)(q-1)?
  5. Nov 25, 2008 #4


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