> Jesse Hammons wrote:
>
>> So to clarify: If I generate a 65-bit key, will I be able to use that
>> 65-bit key to sign any 64-bit value?
>
> Yes, but
Actually, I have found the answer to be "no" :-)
> a 65 bit key won't be very secure AT ALL, it will be
> very easy to factor a modulus that small.
Security is not my goal. This is more of a theoretical exercise that
happens to have a practical application for me.
> Bottom line: asymmetrical
> (public-key) encryption has a fairly large "minimum block size" that
> actually increases as key size increases.
Indeed. I have found experimentally that:
* The minimum signable data quantity in OpenSSL is 1 byte
* The minimum size RSA key that can be used to sign 1 byte is 89 bits
* A signature created using a 64-bit RSA key would create a number 64
bits long, BUT:
- This is not possible to do in OpenSSL because the maximum signable
quantity for a 64
bit RSA key is only a few bits, and OpenSSL input/output is done on
byte boundaries
Do those number sound right?
Thanks,
-Jesse
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