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/*
* Curve25519
* (C) 2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/pk_utils.h>
#include <botan/curve25519.h>
#include <botan/ber_dec.h>
#include <botan/der_enc.h>
namespace Botan {
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<byte> curve25519(const secure_vector<byte>& secret,
const byte pubval[32])
{
secure_vector<byte> out(32);
const int rc = curve25519_donna(&out[0], &secret[0], &pubval[0]);
BOTAN_ASSERT_EQUAL(rc, 0, "Return value of curve25519_donna is ok");
return out;
}
secure_vector<byte> curve25519_basepoint(const secure_vector<byte>& secret)
{
const byte basepoint[32] = { 9 };
return curve25519(secret, basepoint);
}
}
AlgorithmIdentifier Curve25519_PublicKey::algorithm_identifier() const
{
return AlgorithmIdentifier(get_oid(), AlgorithmIdentifier::USE_NULL_PARAM);
}
bool Curve25519_PublicKey::check_key(RandomNumberGenerator&, bool) const
{
return true; // no tests possible?
}
Curve25519_PublicKey::Curve25519_PublicKey(const AlgorithmIdentifier&,
const secure_vector<byte>& key_bits)
{
BER_Decoder(key_bits)
.start_cons(SEQUENCE)
.decode(m_public, OCTET_STRING)
.verify_end()
.end_cons();
size_check(m_public.size(), "public key");
}
std::vector<byte> Curve25519_PublicKey::x509_subject_public_key() const
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(m_public, OCTET_STRING)
.end_cons()
.get_contents_unlocked();
}
Curve25519_PrivateKey::Curve25519_PrivateKey(RandomNumberGenerator& rng)
{
m_private = rng.random_vec(32);
m_public = curve25519_basepoint(m_private);
}
Curve25519_PrivateKey::Curve25519_PrivateKey(const AlgorithmIdentifier&,
const secure_vector<byte>& key_bits,
RandomNumberGenerator& rng)
{
BER_Decoder(key_bits)
.start_cons(SEQUENCE)
.decode(m_public, OCTET_STRING)
.decode(m_private, OCTET_STRING)
.verify_end()
.end_cons();
size_check(m_public.size(), "public key");
size_check(m_private.size(), "private key");
load_check(rng);
}
secure_vector<byte> Curve25519_PrivateKey::pkcs8_private_key() const
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(m_public, OCTET_STRING)
.encode(m_private, OCTET_STRING)
.end_cons()
.get_contents();
}
bool Curve25519_PrivateKey::check_key(RandomNumberGenerator&, bool) const
{
return curve25519_basepoint(m_private) == m_public;
}
secure_vector<byte> Curve25519_PrivateKey::agree(const byte w[], size_t w_len) const
{
size_check(w_len, "public value");
return curve25519(m_private, w);
}
namespace {
/**
* Curve25519 operation
*/
class Curve25519_KA_Operation : public PK_Ops::Key_Agreement_with_KDF
{
public:
typedef Curve25519_PrivateKey Key_Type;
Curve25519_KA_Operation(const Curve25519_PrivateKey& key, const std::string& kdf) :
PK_Ops::Key_Agreement_with_KDF(kdf),
m_key(key) {}
secure_vector<byte> raw_agree(const byte w[], size_t w_len)
{
return m_key.agree(w, w_len);
}
private:
const Curve25519_PrivateKey& m_key;
};
BOTAN_REGISTER_PK_KEY_AGREE_OP("Curve25519", Curve25519_KA_Operation);
}
}
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