# Re: EC Key Derivation Problem

Fabrice <fabrice.gautier@xxxxxxxxx> wrote:
Assuming a EC Private Key "a", and the public key "A=a.P"

I'm looking for a Private Key Derivation Function "f" and a Public Key
Derivation function "F" such that if "b=f(a,k)", then "B=b.P=F(A,k)"

Does such functions exist ?

I'm not really sure about what the point is, but the obvious answer is
that f is multiplication and F is point multiplication...

Actually I am sure they do (by definition) but do they have the
following properties:
- Is the knowledge of F gives any information about a, b, k or f ?
- Is the knowledge of f, k and b gives any information about a ?
- Is the knowledge of F, A and k gives any information about a or b ?
- Is the knowledge of F, B and A gives any information about k, a, or
b ?
- etc...

No, yes, yes, no, etc.

The main purpose is to be able to compute the derived Public Key
without knowing the private root key.

??

--
Kristian Gjøsteen
.

## Relevant Pages

• Re: EC Key Derivation Problem
... I'm looking for a Private Key Derivation Function "f" and a Public Key ... without knowing the private root key. ...
(sci.crypt)
• EC Key Derivation Problem
... I'm looking for a Private Key Derivation Function "f" and a Public Key ... without knowing the private root key. ...
(sci.crypt)