diff --git a/c_src/enacl_nif.c b/c_src/enacl_nif.c index 7326b24..76f344e 100644 --- a/c_src/enacl_nif.c +++ b/c_src/enacl_nif.c @@ -79,6 +79,34 @@ ERL_NIF_TERM enif_crypto_verify_32(ErlNifEnv *env, int argc, ERL_NIF_TERM const } } +/* Curve 25519 */ +static +ERL_NIF_TERM enif_crypto_curve25519_scalarmult(ErlNifEnv *env, int argc, ERL_NIF_TERM const argv[]) { + ErlNifBinary secret, basepoint, output; + uint8_t bp[crypto_scalarmult_curve25519_BYTES]; + + if ((argc != 2) || (!enif_inspect_binary(env, argv[0], &secret)) + || (!enif_inspect_binary(env, argv[1], &basepoint)) + || (secret.size != crypto_scalarmult_curve25519_BYTES) + || (basepoint.size != crypto_scalarmult_curve25519_BYTES)) { + return enif_make_badarg(env); + } + + memcpy(bp, basepoint.data, crypto_scalarmult_curve25519_BYTES); + + /* Clear the high-bit. Better safe than sorry. */ + bp[31] &= 0x7f; + + if (!enif_alloc_binary(crypto_scalarmult_curve25519_BYTES, &output)) { + return nacl_error_tuple(env, "alloc_failed"); + } + + if (crypto_scalarmult_curve25519(output.data, secret.data, bp) < 0) { + return nacl_error_tuple(env, "scalarmult_curve25519_failed"); + } + + return enif_make_binary(env, &output); +} /* Public-key cryptography */ static @@ -806,7 +834,9 @@ static ErlNifFunc nif_funcs[] = { {"crypto_hash", 1, enif_crypto_hash, ERL_NIF_DIRTY_JOB_CPU_BOUND}, {"crypto_verify_16", 2, enif_crypto_verify_16}, {"crypto_verify_32", 2, enif_crypto_verify_32}, - + + {"crypto_curve25519_scalarmult", 2, enif_crypto_curve25519_scalarmult}, + {"randombytes_b", 1, enif_randombytes}, {"randombytes", 1, enif_randombytes, ERL_NIF_DIRTY_JOB_CPU_BOUND}, diff --git a/src/enacl.erl b/src/enacl.erl index 35177c7..8fe12c3 100644 --- a/src/enacl.erl +++ b/src/enacl.erl @@ -67,6 +67,12 @@ verify_32/2 ]). +%% Curve25519 +-export([ + curve25519_keypair/0, + curve25519_shared/2 +]). + %% Libsodium specific functions (which are also part of the "undocumented" interface to NaCl -export([ randombytes/1 @@ -168,6 +174,26 @@ verify_16(_, _) -> error(badarg). verify_32(X, Y) when is_binary(X), is_binary(Y) -> enacl_nif:crypto_verify_32(X, Y); verify_32(_, _) -> error(badarg). +%% Curve 25519 Crypto +%% ------------------ +%% @doc curve25519_keypair/0 creates a new Public/Secret keypair. +%% +%% Generates and returns a new key pair for the Curve 25519 encryption scheme. The return value is a +%% map in order to avoid using the public key as a secret key and vice versa. +%% @end. +-spec curve25519_keypair() -> #{ atom() => binary() }. +curve25519_keypair() -> + <> = randombytes(32), + SK = <<(B0 band 248), B1/binary, (64 bor (B2 band 127))>>, + PK = enacl_nif:crypto_curve25519_scalarmult(SK, <<9, 0:248>>), + #{ public => PK, secret => SK }. + +%% @doc curve25519_shared/2 creates a new shared secret from a given SecretKey and PublicKey. +%% @end. +-spec curve25519_shared(SecretKey :: binary(), PublicKey :: binary()) -> binary(). +curve25519_shared(SecretKey, PublicKey) -> + enacl_nif:crypto_curve25519_scalarmult(SecretKey, PublicKey). + %% Public Key Crypto %% --------------------- %% @doc box_keypair/0 creates a new Public/Secret keypair. diff --git a/src/enacl_nif.erl b/src/enacl_nif.erl index 06f8a0a..e8c4e2e 100644 --- a/src/enacl_nif.erl +++ b/src/enacl_nif.erl @@ -71,6 +71,11 @@ crypto_onetimeauth_verify_b/3 ]). +%% Curve25519 +-export([ + crypto_curve25519_scalarmult/2 +]). + %% Miscellaneous helper functions -export([ crypto_hash/1, @@ -161,6 +166,8 @@ crypto_onetimeauth_b(_Msg, _Key) -> erlang:nif_error(nif_not_loaded). crypto_onetimeauth_verify(_Authenticator, _Msg, _Key) -> erlang:nif_error(nif_not_loaded). crypto_onetimeauth_verify_b(_Authenticator, _Msg, _Key) -> erlang:nif_error(nif_not_loaded). +crypto_curve25519_scalarmult(_Secret, _BasePoint) -> erlang:nif_error(nif_not_loaded). + crypto_hash(Input) when is_binary(Input) -> erlang:nif_error(nif_not_loaded). crypto_hash_b(Input) when is_binary(Input) -> erlang:nif_error(nif_not_loaded). crypto_verify_16(_X, _Y) -> erlang:nif_error(nif_not_loaded).