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/*
* Discrete Logarithm Group
* (C) 1999-2008 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_DL_PARAM_H__
#define BOTAN_DL_PARAM_H__
#include <botan/bigint.h>
#include <botan/data_src.h>
namespace Botan {
/**
* This class represents discrete logarithm groups. It holds a prime p,
* a prime q = (p-1)/2 and g = x^((p-1)/q) mod p.
*/
class BOTAN_DLL DL_Group
{
public:
/**
* Get the prime p.
* @return prime p
*/
const BigInt& get_p() const;
/**
* Get the prime q.
* @return prime q
*/
const BigInt& get_q() const;
/**
* Get the base g.
* @return base g
*/
const BigInt& get_g() const;
/**
* The DL group encoding format variants.
*/
enum Format {
ANSI_X9_42,
ANSI_X9_57,
PKCS_3,
DSA_PARAMETERS = ANSI_X9_57,
DH_PARAMETERS = ANSI_X9_42,
X942_DH_PARAMETERS = ANSI_X9_42,
PKCS3_DH_PARAMETERS = PKCS_3
};
/**
* Determine the prime creation for DL groups.
*/
enum PrimeType { Strong, Prime_Subgroup, DSA_Kosherizer };
/**
* Perform validity checks on the group.
* @param rng the rng to use
* @param strong whether to perform stronger by lengthier tests
* @return true if the object is consistent, false otherwise
*/
bool verify_group(RandomNumberGenerator& rng, bool strong) const;
/**
* Encode this group into a string using PEM encoding.
* @param format the encoding format
* @return string holding the PEM encoded group
*/
std::string PEM_encode(Format format) const;
/**
* Encode this group into a string using DER encoding.
* @param format the encoding format
* @return string holding the DER encoded group
*/
std::vector<byte> DER_encode(Format format) const;
/**
* Decode a DER/BER encoded group into this instance.
* @param ber a vector containing the DER/BER encoded group
* @param format the format of the encoded group
*/
void BER_decode(const std::vector<byte>& ber,
Format format);
/**
* Decode a PEM encoded group into this instance.
* @param pem the PEM encoding of the group
*/
void PEM_decode(const std::string& pem);
/**
* Construct a DL group with uninitialized internal value.
* Use this constructor is you wish to set the groups values
* from a DER or PEM encoded group.
*/
DL_Group();
/**
* Construct a DL group that is registered in the configuration.
* @param name the name that is configured in the global configuration
* for the desired group. If no configuration file is specified,
* the default values from the file policy.cpp will be used. For instance,
* use "modp/ietf/768" as name.
*/
DL_Group(const std::string& name);
/**
* Create a new group randomly.
* @param rng the random number generator to use
* @param type specifies how the creation of primes p and q shall
* be performed. If type=Strong, then p will be determined as a
* safe prime, and q will be chosen as (p-1)/2. If
* type=Prime_Subgroup and qbits = 0, then the size of q will be
* determined according to the estimated difficulty of the DL
* problem. If type=DSA_Kosherizer, DSA primes will be created.
* @param pbits the number of bits of p
* @param qbits the number of bits of q. Leave it as 0 to have
* the value determined according to pbits.
*/
DL_Group(RandomNumberGenerator& rng, PrimeType type,
size_t pbits, size_t qbits = 0);
/**
* Create a DSA group with a given seed.
* @param rng the random number generator to use
* @param seed the seed to use to create the random primes
* @param pbits the desired bit size of the prime p
* @param qbits the desired bit size of the prime q.
*/
DL_Group(RandomNumberGenerator& rng,
const std::vector<byte>& seed,
size_t pbits = 1024, size_t qbits = 0);
/**
* Create a DL group. The prime q will be determined according to p.
* @param p the prime p
* @param g the base g
*/
DL_Group(const BigInt& p, const BigInt& g);
/**
* Create a DL group.
* @param p the prime p
* @param q the prime q
* @param g the base g
*/
DL_Group(const BigInt& p, const BigInt& q, const BigInt& g);
/**
* Return PEM representation of named DL group
*/
static const char* PEM_for_named_group(const std::string& name);
private:
static BigInt make_dsa_generator(const BigInt&, const BigInt&);
void init_check() const;
void initialize(const BigInt&, const BigInt&, const BigInt&);
bool initialized;
BigInt p, q, g;
};
}
#endif
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