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/*
* Curve25519
* (C) 2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/curve25519.h>
#include <botan/internal/pk_ops_impl.h>
#include <botan/ber_dec.h>
#include <botan/der_enc.h>
#include <botan/rng.h>
namespace Botan {
void curve25519_basepoint(uint8_t mypublic[32], const uint8_t secret[32])
{
const uint8_t basepoint[32] = { 9 };
curve25519_donna(mypublic, secret, basepoint);
}
namespace {
void size_check(size_t size, const char* thing)
{
if(size != 32)
throw Decoding_Error("Invalid size " + std::to_string(size) + " for Curve25519 " + thing);
}
secure_vector<uint8_t> curve25519(const secure_vector<uint8_t>& secret,
const uint8_t pubval[32])
{
secure_vector<uint8_t> out(32);
curve25519_donna(out.data(), secret.data(), pubval);
return out;
}
}
AlgorithmIdentifier Curve25519_PublicKey::algorithm_identifier() const
{
return AlgorithmIdentifier(get_oid(), AlgorithmIdentifier::USE_EMPTY_PARAM);
}
bool Curve25519_PublicKey::check_key(RandomNumberGenerator&, bool) const
{
return true; // no tests possible?
}
Curve25519_PublicKey::Curve25519_PublicKey(const AlgorithmIdentifier&,
const std::vector<uint8_t>& key_bits)
{
m_public = key_bits;
size_check(m_public.size(), "public key");
}
std::vector<uint8_t> Curve25519_PublicKey::public_key_bits() const
{
return m_public;
}
Curve25519_PrivateKey::Curve25519_PrivateKey(const secure_vector<uint8_t>& secret_key)
{
if(secret_key.size() != 32)
throw Decoding_Error("Invalid size for Curve25519 private key");
m_public.resize(32);
m_private = secret_key;
curve25519_basepoint(m_public.data(), m_private.data());
}
Curve25519_PrivateKey::Curve25519_PrivateKey(RandomNumberGenerator& rng)
{
m_private = rng.random_vec(32);
m_public.resize(32);
curve25519_basepoint(m_public.data(), m_private.data());
}
Curve25519_PrivateKey::Curve25519_PrivateKey(const AlgorithmIdentifier&,
const secure_vector<uint8_t>& key_bits)
{
BER_Decoder(key_bits).decode(m_private, OCTET_STRING).discard_remaining();
size_check(m_private.size(), "private key");
m_public.resize(32);
curve25519_basepoint(m_public.data(), m_private.data());
}
secure_vector<uint8_t> Curve25519_PrivateKey::private_key_bits() const
{
return DER_Encoder().encode(m_private, OCTET_STRING).get_contents();
}
bool Curve25519_PrivateKey::check_key(RandomNumberGenerator&, bool) const
{
std::vector<uint8_t> public_point(32);
curve25519_basepoint(public_point.data(), m_private.data());
return public_point == m_public;
}
secure_vector<uint8_t> Curve25519_PrivateKey::agree(const uint8_t w[], size_t w_len) const
{
size_check(w_len, "public value");
return curve25519(m_private, w);
}
namespace {
/**
* Curve25519 operation
*/
class Curve25519_KA_Operation final : public PK_Ops::Key_Agreement_with_KDF
{
public:
Curve25519_KA_Operation(const Curve25519_PrivateKey& key, const std::string& kdf) :
PK_Ops::Key_Agreement_with_KDF(kdf),
m_key(key) {}
size_t agreed_value_size() const override { return 32; }
secure_vector<uint8_t> raw_agree(const uint8_t w[], size_t w_len) override
{
return m_key.agree(w, w_len);
}
private:
const Curve25519_PrivateKey& m_key;
};
}
std::unique_ptr<PK_Ops::Key_Agreement>
Curve25519_PrivateKey::create_key_agreement_op(RandomNumberGenerator& /*rng*/,
const std::string& params,
const std::string& provider) const
{
if(provider == "base" || provider.empty())
return std::unique_ptr<PK_Ops::Key_Agreement>(new Curve25519_KA_Operation(*this, params));
throw Provider_Not_Found(algo_name(), provider);
}
}