Re: question about rsa encryption

[Pete Chown]

Scott G. Kelly wrote:

I seem to recall reading somewhere that there is some issue with
directly encrypting data with an RSA public key, perhaps some
vulnerability, but I can't find any reference after a cursory look.

There are a few different ones, some simple and some complex. First of all, imagine encrypting 0 or 1. Encryption leaves these numbers unchanged. Now, if each possible plaintext had equal probability, this would be extremely unlikely. However, in practice it is likely that users may want to encrypt small numbers.

Another problem is that RSA encryptions multiply. If r(x) is the encryption operation, then r(x) r(y) = r(xy). Informally:

r(x) r(y) = (x ** e) (y ** e)
= x * x * x * ... * y * y * y
= xy * xy * ... * xy
= (xy) ** e
= r(xy)

I think there are a few others too...

--
Pete


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