Take the 2-minute tour ×
Cryptography Stack Exchange is a question and answer site for software developers, mathematicians and others interested in cryptography. It's 100% free, no registration required.

Why are security against eavesdropping and security against CPA equivalent in the setting of public-key cryptography?

share|improve this question
    
It seems to me a homework question more than research one. –  AntonioFa Dec 16 '13 at 10:23

1 Answer 1

up vote 4 down vote accepted

Under a chosen-plaintext attack, the adversary has the power to encrypt polynomially-many chosen plaintexts. In the symmetric world, since only the valid parties hold the encryption key, only the valid parties can "grant" the adversary access to an encryption oracle. So, it isn't assumed that an eavesdropper necessarily has access to an encryption oracle.

In the asymmetric world, however, the public key — the key used to encrypt data — is, well, public. So, an eavesdropper overhears the public key (or is simply assumed to know it, since it is public), and from there the eavesdropper may encrypt whatever messages he or she so desires. This is the same scenario as a chosen-plaintext attack.

share|improve this answer

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.