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// xed25519_32.cpp - written and placed in public domain by Jeffrey Walton
// Crypto++ specific implementation wrapped around Adam
// Langley's curve25519-donna.
#include "pch.h"
#include "cryptlib.h"
#include "asn.h"
#include "integer.h"
#include "filters.h"
#include "xed25519.h"
#include "donna.h"
ANONYMOUS_NAMESPACE_BEGIN
using CryptoPP::byte;
CRYPTOPP_ALIGN_DATA(16)
const byte blacklist[][32] = {
{ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
{ 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 },
{ 0xe0, 0xeb, 0x7a, 0x7c, 0x3b, 0x41, 0xb8, 0xae, 0x16, 0x56, 0xe3, 0xfa, 0xf1, 0x9f, 0xc4, 0x6a,
0xda, 0x09, 0x8d, 0xeb, 0x9c, 0x32, 0xb1, 0xfd, 0x86, 0x62, 0x05, 0x16, 0x5f, 0x49, 0xb8, 0x00 },
{ 0x5f, 0x9c, 0x95, 0xbc, 0xa3, 0x50, 0x8c, 0x24, 0xb1, 0xd0, 0xb1, 0x55, 0x9c, 0x83, 0xef, 0x5b,
0x04, 0x44, 0x5c, 0xc4, 0x58, 0x1c, 0x8e, 0x86, 0xd8, 0x22, 0x4e, 0xdd, 0xd0, 0x9f, 0x11, 0x57 },
{ 0xec, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
{ 0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
{ 0xee, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
{ 0xcd, 0xeb, 0x7a, 0x7c, 0x3b, 0x41, 0xb8, 0xae, 0x16, 0x56, 0xe3, 0xfa, 0xf1, 0x9f, 0xc4, 0x6a,
0xda, 0x09, 0x8d, 0xeb, 0x9c, 0x32, 0xb1, 0xfd, 0x86, 0x62, 0x05, 0x16, 0x5f, 0x49, 0xb8, 0x80 },
{ 0x4c, 0x9c, 0x95, 0xbc, 0xa3, 0x50, 0x8c, 0x24, 0xb1, 0xd0, 0xb1, 0x55, 0x9c, 0x83, 0xef, 0x5b,
0x04, 0x44, 0x5c, 0xc4, 0x58, 0x1c, 0x8e, 0x86, 0xd8, 0x22, 0x4e, 0xdd, 0xd0, 0x9f, 0x11, 0xd7 },
{ 0xd9, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
{ 0xda, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
{ 0xdb, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }
};
ANONYMOUS_NAMESPACE_END
NAMESPACE_BEGIN(CryptoPP)
bool x25519::IsClamped(const byte x[32])
{
return (x[0] & 248) == x[0] && (x[31] & 127) == x[31] && (x[31] | 64) == x[31];
}
// See the comments for the code in tweetnacl.cpp
bool x25519::IsSmallOrder(const byte y[32])
{
// The magic 12 is the count of blaklisted points
byte c[12] = { 0 };
for (size_t j = 0; j < 32; j++) {
for (size_t i = 0; i < COUNTOF(blacklist); i++) {
c[i] |= y[j] ^ blacklist[i][j];
}
}
unsigned int k = 0;
for (size_t i = 0; i < COUNTOF(blacklist); i++) {
k |= (c[i] - 1);
}
return (bool) ((k >> 8) & 1);
}
void x25519::ClampKey(byte x[32])
{
x[0] &= 248;
x[31] &= 127;
x[31] |= 64;
}
x25519::x25519(const byte y[32], const byte x[32])
{
std::memcpy(m_pk, y, 32);
std::memcpy(m_sk, x, 32);
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
}
x25519::x25519(const byte x[32])
{
std::memcpy(m_sk, x, 32);
GeneratePublicKey(NullRNG(), m_sk, m_pk);
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
}
x25519::x25519(const Integer &y, const Integer &x)
{
ArraySink ys(m_pk, 32);
y.Encode(ys, 32);
ArraySink xs(m_sk, 32);
x.Encode(xs, 32);
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
}
x25519::x25519(const Integer &x)
{
ArraySink xs(m_sk, 32);
x.Encode(xs, 32);
GeneratePublicKey(NullRNG(), m_sk, m_pk);
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
}
x25519::x25519(RandomNumberGenerator &rng)
{
GeneratePrivateKey(rng, m_sk);
GeneratePublicKey(NullRNG(), m_sk, m_pk);
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
}
x25519::x25519(BufferedTransformation ¶ms)
{
// TODO: Fix the on-disk format once we determine what it is.
BERSequenceDecoder seq(params);
size_t read; byte unused;
BERSequenceDecoder sk(seq, BIT_STRING);
CRYPTOPP_ASSERT(sk.MaxRetrievable() >= 33);
read = sk.Get(unused); // unused bits
CRYPTOPP_ASSERT(read == 1 && unused == 0);
read = sk.Get(m_sk, 32);
sk.MessageEnd();
if (read != 32)
throw BERDecodeErr();
if (seq.EndReached())
{
GeneratePublicKey(NullRNG(), m_sk, m_pk);
}
else
{
BERSequenceDecoder pk(seq, OCTET_STRING);
CRYPTOPP_ASSERT(pk.MaxRetrievable() >= 32);
read = pk.Get(m_pk, 32);
pk.MessageEnd();
if (read != 32)
throw BERDecodeErr();
}
seq.MessageEnd();
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
}
void x25519::DEREncode(BufferedTransformation ¶ms) const
{
// TODO: Fix the on-disk format once we determine what it is.
DERSequenceEncoder seq(params);
DERSequenceEncoder sk(seq, BIT_STRING);
sk.Put((byte)0); // unused bits
sk.Put(m_sk, 32);
sk.MessageEnd();
DERSequenceEncoder pk(seq, OCTET_STRING);
pk.Put(m_pk, 32);
pk.MessageEnd();
seq.MessageEnd();
}
bool x25519::Validate(RandomNumberGenerator &rng, unsigned int level) const
{
CRYPTOPP_UNUSED(rng);
CRYPTOPP_ASSERT(IsClamped(m_sk) == true);
CRYPTOPP_ASSERT(IsSmallOrder(m_pk) == false);
if (level >= 1 && IsClamped(m_sk) == false)
return false;
if (level >= 2 && IsSmallOrder(m_pk) == true)
return false;
return true;
}
bool x25519::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
{
if (valueType == typeid(ConstByteArrayParameter))
{
if (std::strcmp(name, "SecretKey") == 0)
{
std::memcpy(pValue, m_sk, 32);
return true;
}
else if (std::strcmp(name, "PublicKey") == 0)
{
std::memcpy(pValue, m_pk, 32);
return true;
}
}
return false;
}
void x25519::AssignFrom(const NameValuePairs &source)
{
ConstByteArrayParameter val;
if (source.GetValue("SecretKey", val))
{
std::memcpy(m_sk, val.begin(), 32);
}
else if (source.GetValue("PublicKey", val))
{
std::memcpy(m_pk, val.begin(), 32);
}
}
void x25519::GeneratePrivateKey(RandomNumberGenerator &rng, byte *privateKey) const
{
rng.GenerateBlock(privateKey, 32);
ClampKey(privateKey);
}
void x25519::GeneratePublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const
{
CRYPTOPP_UNUSED(rng);
(void)Donna::curve25519(publicKey, privateKey);
}
bool x25519::Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey) const
{
CRYPTOPP_ASSERT(agreedValue != NULLPTR);
CRYPTOPP_ASSERT(otherPublicKey != NULLPTR);
if (validateOtherPublicKey && IsSmallOrder(otherPublicKey))
return false;
return Donna::curve25519(agreedValue, privateKey, otherPublicKey) == 0;
}
NAMESPACE_END // CryptoPP
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