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Re: [freehaven-dev] Literature repository, multi-e/single-d crypto scheme

dmolnar@belegost.mit.edu writes:

> On Sun, 7 May 2000, Michael J Freedman wrote:
> >   A message M is encrypted by keys {e_1 ... e_n}
> >   M can be decrypted by any d_i \element {d_1 ... d_n}, 
> >       the corresponding private keys.
> The most straightforward solution here is to encrypt M a total of n times,
> each time with a separate public key e_i. Concatenate together and pass
> around. Then any single d_i can decrypt the corresponding encrypted
> message and recover the message. I think this is what PGP does. 

PGP actually uses wth hybrid system you mention below.  The symmetric
cipher is IDEA, and the public key is either RSA or ElGamal.

> 	1) Generate random symmetric key K 128 bits long. 
> 	2) Encrypt M with K -- E_K(M).
> 	3) Encrypt K with public keys e_1 -- e_n
> 	4) Concatenate encrypted Ks and E_K(M)