void PEM_DH_Load(BufferedTransformation& bt, Integer& p, Integer& q, Integer& g)
{
ByteQueue obj;
PEM_NextObject(bt, obj);
PEM_Type type = PEM_GetType(obj);
if(type == PEM_DH_PARAMETERS)
PEM_StripEncapsulatedBoundary(obj, SBB_DH_PARAMETERS_BEGIN, SBB_DH_PARAMETERS_END);
else
throw InvalidDataFormat("PEM_DH_Read: invalid DH parameters");
ByteQueue temp;
PEM_Base64Decode(obj, temp);
BERSequenceDecoder dh(temp);
p.BERDecode(dh);
q.BERDecode(dh);
g.BERDecode(dh);
dh.MessageEnd();
#if PEM_KEY_OR_PARAMETER_VALIDATION
AutoSeededRandomPool prng;
if(!VerifyPrime(prng, p, 3))
throw Exception(Exception::OTHER_ERROR, "PEM_DH_Read: p is not prime");
// https://crypto.stackexchange.com/questions/12961/diffie-hellman-parameter-check-when-g-2-must-p-mod-24-11
long residue = p % 24;
if(residue != 11 && residue != 23)
throw Exception(Exception::OTHER_ERROR, "PEM_DH_Read: g is not a suitable generator");
#endif
}
void DL_GroupParameters_EC<EC>::BERDecode(BufferedTransformation &bt)
{
byte b;
if (!bt.Peek(b))
BERDecodeError();
if (b == OBJECT_IDENTIFIER)
Initialize(OID(bt));
else
{
BERSequenceDecoder seq(bt);
word32 version;
BERDecodeUnsigned<word32>(seq, version, INTEGER, 1, 1); // check version
EllipticCurve ec(seq);
Point G = ec.BERDecodePoint(seq);
Integer n(seq);
Integer k;
bool cofactorPresent = !seq.EndReached();
if (cofactorPresent)
k.BERDecode(seq);
else
k = Integer::Zero();
seq.MessageEnd();
Initialize(ec, G, n, k);
}
}