RSA questions

[Karl Lui Barrus]

Karl Lui Barrus wrote:
>Hm.... I don't think you reduce the keyspace all that much.  The
>restriction on e (and d) is they must be relatively prime to phi(n),
>and if n = p q = (2p' + 1) (2q' + 1) then phi(n) = 4p'q', in which
>case e (and d) can't be 2, 4, p', q', 2p', 2q', 4p', 4q', or 4p'q', a
>total of 9 numbers out of the total possible.  I don't remember the

Argh, I left out p'q' and 2p'q', which brings the total to 11 unusable
numbers. 

-- 
Karl L. Barrus: klbarrus at owlnet.rice.edu         
keyID: 5AD633 hash: D1 59 9D 48 72 E9 19 D5  3D F3 93 7E 81 B5 CC 32 

"One man's mnemonic is another man's cryptography" 
  - my compilers prof discussing file naming in public directories