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# xtrcrypt.cpp

    00001 // xtrcrypt.cpp - written and placed in the public domain by Wei Dai
    00002
    00003 #include "pch.h"
    00004 #include "xtrcrypt.h"
    00005 #include "nbtheory.h"
    00006 #include "asn.h"
    00007 #include "argnames.h"
    00008
    00009 NAMESPACE_BEGIN(CryptoPP)
    00010
    00011 XTR_DH::XTR_DH(const Integer &p, const Integer &q, const GFP2Element &g)
    00012         : m_p(p), m_q(q), m_g(g)
    00013 {
    00014 }
    00015
    00016 XTR_DH::XTR_DH(RandomNumberGenerator &rng, unsigned int pbits, unsigned int qbits)
    00017 {
    00018         XTR_FindPrimesAndGenerator(rng, m_p, m_q, m_g, pbits, qbits);
    00019 }
    00020
    00021 XTR_DH::XTR_DH(BufferedTransformation &bt)
    00022 {
    00023         BERSequenceDecoder seq(bt);
    00024         m_p.BERDecode(seq);
    00025         m_q.BERDecode(seq);
    00026         m_g.c1.BERDecode(seq);
    00027         m_g.c2.BERDecode(seq);
    00028         seq.MessageEnd();
    00029 }
    00030
    00031 void XTR_DH::DEREncode(BufferedTransformation &bt) const
    00032 {
    00033         DERSequenceEncoder seq(bt);
    00034         m_p.DEREncode(seq);
    00035         m_q.DEREncode(seq);
    00036         m_g.c1.DEREncode(seq);
    00037         m_g.c2.DEREncode(seq);
    00038         seq.MessageEnd();
    00039 }
    00040
    00041 bool XTR_DH::Validate(RandomNumberGenerator &rng, unsigned int level) const
    00042 {
    00043         bool pass = true;
    00044         pass = pass && m_p > Integer::One() && m_p.IsOdd();
    00045         pass = pass && m_q > Integer::One() && m_q.IsOdd();
    00046         GFP2Element three = GFP2_ONB<ModularArithmetic>(m_p).ConvertIn(3);
    00047         pass = pass && !(m_g.c1.IsNegative() || m_g.c2.IsNegative() || m_g.c1 >= m_p || m_g.c2 >= m_p || m_g == three);
    00048         if (level >= 1)
    00049                 pass = pass && ((m_p.Squared()-m_p+1)%m_q).IsZero();
    00050         if (level >= 2)
    00051         {
    00052                 pass = pass && VerifyPrime(rng, m_p, level-2) && VerifyPrime(rng, m_q, level-2);
    00053                 pass = pass && XTR_Exponentiate(m_g, (m_p.Squared()-m_p+1)/m_q, m_p) != three;
    00054                 pass = pass && XTR_Exponentiate(m_g, m_q, m_p) == three;
    00055         }
    00056         return pass;
    00057 }
    00058
    00059 bool XTR_DH::GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
    00060 {
    00061         return GetValueHelper(this, name, valueType, pValue).Assignable()
    00062                 CRYPTOPP_GET_FUNCTION_ENTRY(Modulus)
    00063                 CRYPTOPP_GET_FUNCTION_ENTRY(SubgroupOrder)
    00064                 CRYPTOPP_GET_FUNCTION_ENTRY(SubgroupGenerator)
    00065                 ;
    00066 }
    00067
    00068 void XTR_DH::AssignFrom(const NameValuePairs &source)
    00069 {
    00070         AssignFromHelper(this, source)
    00071                 CRYPTOPP_SET_FUNCTION_ENTRY(Modulus)
    00072                 CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupOrder)
    00073                 CRYPTOPP_SET_FUNCTION_ENTRY(SubgroupGenerator)
    00074                 ;
    00075 }
    00076
    00077 void XTR_DH::GeneratePrivateKey(RandomNumberGenerator &rng, byte *privateKey) const
    00078 {
    00079         Integer x(rng, Integer::Zero(), m_q-1);
    00080         x.Encode(privateKey, PrivateKeyLength());
    00081 }
    00082
    00083 void XTR_DH::GeneratePublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const
    00084 {
    00085         Integer x(privateKey, PrivateKeyLength());
    00086         GFP2Element y = XTR_Exponentiate(m_g, x, m_p);
    00087         y.Encode(publicKey, PublicKeyLength());
    00088 }
    00089
    00090 bool XTR_DH::Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey) const
    00091 {
    00092         GFP2Element w(otherPublicKey, PublicKeyLength());
    00093         if (validateOtherPublicKey)
    00094         {
    00095                 GFP2_ONB<ModularArithmetic> gfp2(m_p);
    00096                 GFP2Element three = gfp2.ConvertIn(3);
    00097                 if (w.c1.IsNegative() || w.c2.IsNegative() || w.c1 >= m_p || w.c2 >= m_p || w == three)
    00098                         return false;
    00099                 if (XTR_Exponentiate(w, m_q, m_p) != three)
    00100                         return false;
    00101         }
    00102         Integer s(privateKey, PrivateKeyLength());
    00103         GFP2Element z = XTR_Exponentiate(w, s, m_p);
    00104         z.Encode(agreedValue, AgreedValueLength());
    00105         return true;
    00106 }
    00107
    00108 NAMESPACE_END