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/*************************************************
* Discrete Logarithm Parameters Source File *
* (C) 1999-2007 The Botan Project *
*************************************************/
#include <botan/dl_group.h>
#include <botan/config.h>
#include <botan/parsing.h>
#include <botan/numthry.h>
#include <botan/der_enc.h>
#include <botan/ber_dec.h>
#include <botan/pipe.h>
#include <botan/util.h>
#include <botan/pem.h>
namespace Botan {
/*************************************************
* DL_Group Constructor *
*************************************************/
DL_Group::DL_Group()
{
initialized = false;
}
/*************************************************
* DL_Group Constructor *
*************************************************/
DL_Group::DL_Group(const std::string& type)
{
DataSource_Memory pem(global_config().get("dl", type));
PEM_decode(pem);
}
/*************************************************
* DL_Group Constructor *
*************************************************/
DL_Group::DL_Group(u32bit pbits, PrimeType type)
{
if(pbits < 512)
throw Invalid_Argument("DL_Group: prime size " + to_string(pbits) +
" is too small");
if(type == Strong)
{
p = random_safe_prime(pbits);
q = (p - 1) / 2;
g = 2;
}
else if(type == Prime_Subgroup || type == DSA_Kosherizer)
{
if(type == Prime_Subgroup)
{
const u32bit qbits = 2 * dl_work_factor(pbits);
q = random_prime(qbits);
BigInt X;
while(p.bits() != pbits || !is_prime(p))
{
X = random_integer(pbits);
p = X - (X % (2*q) - 1);
}
}
else
generate_dsa_primes(p, q, pbits);
g = make_dsa_generator(p, q);
}
initialized = true;
}
/*************************************************
* DL_Group Constructor *
*************************************************/
DL_Group::DL_Group(const MemoryRegion<byte>& seed, u32bit pbits, u32bit start)
{
if(!generate_dsa_primes(p, q, seed.begin(), seed.size(), pbits, start))
throw Invalid_Argument("DL_Group: The seed/counter given does not "
"generate a DSA group");
g = make_dsa_generator(p, q);
initialized = true;
}
/*************************************************
* DL_Group Constructor *
*************************************************/
DL_Group::DL_Group(const BigInt& p1, const BigInt& g1)
{
initialize(p1, 0, g1);
}
/*************************************************
* DL_Group Constructor *
*************************************************/
DL_Group::DL_Group(const BigInt& p1, const BigInt& q1, const BigInt& g1)
{
initialize(p1, q1, g1);
}
/*************************************************
* DL_Group Initializer *
*************************************************/
void DL_Group::initialize(const BigInt& p1, const BigInt& q1, const BigInt& g1)
{
if(p1 < 3)
throw Invalid_Argument("DL_Group: Prime invalid");
if(g1 < 2 || g1 >= p1)
throw Invalid_Argument("DL_Group: Generator invalid");
if(q1 < 0 || q1 >= p1)
throw Invalid_Argument("DL_Group: Subgroup invalid");
p = p1;
g = g1;
q = q1;
if(q == 0 && check_prime((p - 1) / 2))
q = (p - 1) / 2;
initialized = true;
}
/*************************************************
* Verify that the group has been set *
*************************************************/
void DL_Group::init_check() const
{
if(!initialized)
throw Invalid_State("DLP group cannot be used uninitialized");
}
/*************************************************
* Verify the parameters *
*************************************************/
bool DL_Group::verify_group(bool strong) const
{
init_check();
if(g < 2 || p < 3 || q < 0)
return false;
if((q != 0) && ((p - 1) % q != 0))
return false;
if(!strong)
return true;
if(!check_prime(p))
return false;
if((q > 0) && !check_prime(q))
return false;
return true;
}
/*************************************************
* Return the prime *
*************************************************/
const BigInt& DL_Group::get_p() const
{
init_check();
return p;
}
/*************************************************
* Return the generator *
*************************************************/
const BigInt& DL_Group::get_g() const
{
init_check();
return g;
}
/*************************************************
* Return the subgroup *
*************************************************/
const BigInt& DL_Group::get_q() const
{
init_check();
if(q == 0)
throw Format_Error("DLP group has no q prime specified");
return q;
}
/*************************************************
* DER encode the parameters *
*************************************************/
SecureVector<byte> DL_Group::DER_encode(Format format) const
{
init_check();
if((q == 0) && (format != PKCS_3))
throw Encoding_Error("The ANSI DL parameter formats require a subgroup");
if(format == ANSI_X9_57)
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(p)
.encode(q)
.encode(g)
.end_cons()
.get_contents();
}
else if(format == ANSI_X9_42)
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(p)
.encode(g)
.encode(q)
.end_cons()
.get_contents();
}
else if(format == PKCS_3)
{
return DER_Encoder()
.start_cons(SEQUENCE)
.encode(p)
.encode(g)
.end_cons()
.get_contents();
}
throw Invalid_Argument("Unknown DL_Group encoding " + to_string(format));
}
/*************************************************
* PEM encode the parameters *
*************************************************/
std::string DL_Group::PEM_encode(Format format) const
{
SecureVector<byte> encoding = DER_encode(format);
if(format == PKCS_3)
return PEM_Code::encode(encoding, "DH PARAMETERS");
else if(format == ANSI_X9_57)
return PEM_Code::encode(encoding, "DSA PARAMETERS");
else if(format == ANSI_X9_42)
return PEM_Code::encode(encoding, "X942 DH PARAMETERS");
else
throw Invalid_Argument("Unknown DL_Group encoding " + to_string(format));
}
/*************************************************
* Decode BER encoded parameters *
*************************************************/
void DL_Group::BER_decode(DataSource& source, Format format)
{
BigInt new_p, new_q, new_g;
BER_Decoder decoder(source);
BER_Decoder ber = decoder.start_cons(SEQUENCE);
if(format == ANSI_X9_57)
{
ber.decode(new_p)
.decode(new_q)
.decode(new_g)
.verify_end();
}
else if(format == ANSI_X9_42)
{
ber.decode(new_p)
.decode(new_g)
.decode(new_q)
.discard_remaining();
}
else if(format == PKCS_3)
{
ber.decode(new_p)
.decode(new_g)
.discard_remaining();
}
else
throw Invalid_Argument("Unknown DL_Group encoding " + to_string(format));
initialize(new_p, new_q, new_g);
}
/*************************************************
* Decode PEM encoded parameters *
*************************************************/
void DL_Group::PEM_decode(DataSource& source)
{
std::string label;
DataSource_Memory ber(PEM_Code::decode(source, label));
if(label == "DH PARAMETERS")
BER_decode(ber, PKCS_3);
else if(label == "DSA PARAMETERS")
BER_decode(ber, ANSI_X9_57);
else if(label == "X942 DH PARAMETERS")
BER_decode(ber, ANSI_X9_42);
else
throw Decoding_Error("DL_Group: Invalid PEM label " + label);
}
/*************************************************
* Create a random DSA-style generator *
*************************************************/
BigInt DL_Group::make_dsa_generator(const BigInt& p, const BigInt& q)
{
BigInt g, e = (p - 1) / q;
for(u32bit j = 0; j != PRIME_TABLE_SIZE; ++j)
{
g = power_mod(PRIMES[j], e, p);
if(g != 1)
break;
}
if(g == 1)
throw Exception("DL_Group: Couldn't create a suitable generator");
return g;
}
}
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