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Implementations of a fast Elliptic-curve Diffie-Hellman primitive
C Python Java Makefile Other
Branch: master

Merge pull request #34 from coruus/patch-1

Recommend pubkey inclusion in key derivation
latest commit 25e77fb5c7
@agl authored

README

See http://code.google.com/p/curve25519-donna/ for details.

BUILDING:

If you run `make`, two .a archives will be built, similar to djb's curve25519
code. Alternatively, read on:

The C implementation is contained within curve25519-donna.c. It has no external
dependancies and is BSD licenced. You can copy/include/link it directly in with
your program. Recommended C flags: -O2

The x86-64 bit implementation is contained within curve25519-donna-x86-64.c and
curve25519-donna-x86-64.s. Build like this:

% cpp curve25519-donna-x86-64.s > curve25519-donna-x86-64.s.pp
% as -o curve25519-donna-x86-64.s.o curve25519-donna-x86-64.s.pp
% gcc -O2 -c curve25519-donna-x86-64.c

Then the two .o files can be linked in

USAGE:

The usage is exactly the same as djb's code (as described at
http://cr.yp.to/ecdh.html) expect that the function is called curve25519_donna.

In short:

To generate a private key just generate 32 random bytes.

To generate the public key, just do:

  static const uint8_t basepoint[32] = {9};
  curve25519_donna(mypublic, mysecret, basepoint);

To generate a shared secret do:

  uint8_t shared[32];
  curve25519_donna(shared, mysecret, theirpublic);

And hash the sender's public key, the recipient's public key, and shared_key
with a cryptographic hash function before using.
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