Re: Need simple lib for asymetric encryption


"Unruh" <unruh-spam@xxxxxxxxxxxxxx> wrote in message
news:ebctul$p2m$1@xxxxxxxxxxxxxxxxxxxxxxxxx
"amzoti" <amzoti@xxxxxxxxx> writes:


Oliver Eichler wrote:
Hi,

I am not a crypto specialist, thus please forgive me if I sound a
little bit
clueless.

I would like to encrypt some data with key1 and decrypt it again with
key2.
If I got it right from all the stuff I have read so far you refere to
key1
as 'public key' and to key2 as 'private key'. Normally the public key
is
generated from the private key. Thus, who got the private key can
always
generate the public key. Is this mandatory?

Public key crypto is abysmally slow. Noone ever actually encrypts data
with
a public key. They encrypt a random key for symmetric key crypto (ie the
same key encrypts and decrypts loosely speaking) and use that much faster
symmetric crypto to actually encrypt the data.

Since one HAS to generate both the encryption and decryption key and has
to
make sure that the decryption key actually decrypts and that it is not
derivable from any public data, it would seem that the only way is to
derive the public key from the private, or at least both from some other
private data.


What algorithm would I need to satisfy my needs? And is there a simple
to
use, light weight C library?

RSA, DSA, Elliptic curve crypto.


I have looked into cryptlib, beecrypt and others.But they all seem to
be an
overkill to my problem with a quite hard to understand API. Isn't there
something like :

I think that maybe you need to learn more before trying to impliment
crypto. The algorithm is the least of your worries. Key control is a far
worse worry.

Could you elaborate on that? Once generated you simply store the keys
somewhere on the disk, right?



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