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/*
* ECC Key implemenation
* (C) 2007 Manuel Hartl, FlexSecure GmbH
* Falko Strenzke, FlexSecure GmbH
* 2008-2010 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/ecc_key.h>
#include <botan/x509_key.h>
#include <botan/numthry.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/secmem.h>
#include <botan/point_gfp.h>
#include <botan/workfactor.h>
namespace Botan {
size_t EC_PublicKey::key_length() const
{
return domain().get_curve().get_p().bits();
}
size_t EC_PublicKey::estimated_strength() const
{
return ecp_work_factor(key_length());
}
EC_PublicKey::EC_PublicKey(const EC_Group& dom_par,
const PointGFp& pub_point) :
m_domain_params(dom_par), m_public_key(pub_point),
m_domain_encoding(EC_DOMPAR_ENC_EXPLICIT)
{
if(domain().get_curve() != public_point().get_curve())
throw Invalid_Argument("EC_PublicKey: curve mismatch in constructor");
}
EC_PublicKey::EC_PublicKey(const AlgorithmIdentifier& alg_id,
const std::vector<uint8_t>& key_bits) :
m_domain_params{EC_Group(alg_id.parameters)},
m_public_key{OS2ECP(key_bits, domain().get_curve())},
m_domain_encoding{EC_DOMPAR_ENC_EXPLICIT}
{}
bool EC_PublicKey::check_key(RandomNumberGenerator& rng,
bool) const
{
//verify domain parameters
if(!m_domain_params.verify_group(rng))
{
return false;
}
//check that public point is not at infinity
if(public_point().is_zero())
{
return false;
}
//check that public point is on the curve
if(!public_point().on_the_curve())
{
return false;
}
if(m_domain_params.get_cofactor() > 1)
{
if((public_point() * m_domain_params.get_cofactor()).is_zero())
{
return false;
}
//check that public point has order q
if(!(public_point() * m_domain_params.get_order()).is_zero())
{
return false;
}
}
return true;
}
AlgorithmIdentifier EC_PublicKey::algorithm_identifier() const
{
return AlgorithmIdentifier(get_oid(), DER_domain());
}
std::vector<uint8_t> EC_PublicKey::public_key_bits() const
{
return unlock(EC2OSP(public_point(), PointGFp::COMPRESSED));
}
void EC_PublicKey::set_parameter_encoding(EC_Group_Encoding form)
{
if(form != EC_DOMPAR_ENC_EXPLICIT &&
form != EC_DOMPAR_ENC_IMPLICITCA &&
form != EC_DOMPAR_ENC_OID)
throw Invalid_Argument("Invalid encoding form for EC-key object specified");
if((form == EC_DOMPAR_ENC_OID) && (m_domain_params.get_oid() == ""))
throw Invalid_Argument("Invalid encoding form OID specified for "
"EC-key object whose corresponding domain "
"parameters are without oid");
m_domain_encoding = form;
}
const BigInt& EC_PrivateKey::private_value() const
{
if(m_private_key == 0)
throw Invalid_State("EC_PrivateKey::private_value - uninitialized");
return m_private_key;
}
/**
* EC_PrivateKey constructor
*/
EC_PrivateKey::EC_PrivateKey(RandomNumberGenerator& rng,
const EC_Group& ec_group,
const BigInt& x,
bool with_modular_inverse)
{
m_domain_params = ec_group;
m_domain_encoding = EC_DOMPAR_ENC_EXPLICIT;
if(x == 0)
{
m_private_key = BigInt::random_integer(rng, 1, domain().get_order());
}
else
{
m_private_key = x;
}
m_public_key = domain().get_base_point() *
((with_modular_inverse) ? inverse_mod(m_private_key, m_domain_params.get_order()) : m_private_key);
BOTAN_ASSERT(m_public_key.on_the_curve(),
"Generated public key point was on the curve");
}
secure_vector<uint8_t> EC_PrivateKey::private_key_bits() const
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(static_cast<size_t>(1))
.encode(BigInt::encode_1363(m_private_key, m_private_key.bytes()),
OCTET_STRING)
.end_cons()
.get_contents();
}
EC_PrivateKey::EC_PrivateKey(const AlgorithmIdentifier& alg_id,
const secure_vector<uint8_t>& key_bits,
bool with_modular_inverse)
{
m_domain_params = EC_Group(alg_id.parameters);
m_domain_encoding = EC_DOMPAR_ENC_EXPLICIT;
OID key_parameters;
secure_vector<uint8_t> public_key_bits;
BER_Decoder(key_bits)
.start_cons(SEQUENCE)
.decode_and_check<size_t>(1, "Unknown version code for ECC key")
.decode_octet_string_bigint(m_private_key)
.decode_optional(key_parameters, ASN1_Tag(0), PRIVATE)
.decode_optional_string(public_key_bits, BIT_STRING, 1, PRIVATE)
.end_cons();
if(!key_parameters.empty() && key_parameters != alg_id.oid)
throw Decoding_Error("EC_PrivateKey - inner and outer OIDs did not match");
if(public_key_bits.empty())
{
m_public_key = domain().get_base_point() *
((with_modular_inverse) ? inverse_mod(m_private_key, m_domain_params.get_order()) : m_private_key);
BOTAN_ASSERT(m_public_key.on_the_curve(),
"Public point derived from loaded key was on the curve");
}
else
{
m_public_key = OS2ECP(public_key_bits, domain().get_curve());
// OS2ECP verifies that the point is on the curve
}
}
}
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