Question

Suppose that Bob, very concerned with security, selects an encrypting modulus n=pq where p and q are large primes. Suppose he also chooses two encrypting exponents e₁ and e₂. He asks people sending him messages to “double encrypt” their messages as follows. For each plain text (an element of Zn), he asks them to encrypt it using RSA with modulus n and encrypting exponent e₁, and then encrypt the result of that using RSA with modulus n and encrypting exponent e₂. He thinks he’s getting twice as much security this way. Explain why he is wrong.Is he actually getting less securty? Is there a variation that (plausibly) does give twice as much security?

Answer 1

Cona the e hon e,er the t invtnseone