Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

RSA user Alice has a public key ($n_A=pq$,$e_A$), where $p$ and $q$ are different primes such that the least common multiple $l$ of $p-1$ and $q-1$ is relatively small (i.e. $l$ is close to max($p-1,q-1$)). Explain why, even without factoring $n_A$, a cryptanalyst would quickly find a decryption key $d_A$ for Alice's public key.

Help is greatly appreciated. :)

share|improve this question

1 Answer 1

Without giving away the answer (so you can explore it), here is a huge hint:

  • Fermat's "Difference of Squares Method"
share|improve this answer
    
Crypto! Yay for you! +1 –  amWhy Apr 30 '13 at 0:36
    
@amWhy: I wonder if s/he got the hint? Regards –  Amzoti Apr 30 '13 at 0:38

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.