Hello!
I have PKCS#3 encoded data.
42:d=5 hl=4 l= 267 cons: SEQUENCE
46:d=6 hl=3 l= 129 prim: INTEGER: ...
178:d=6 hl=3 l= 128 prim: INTEGER: ...
309:d=6 hl=2 l= 2 prim: INTEGER: ...
This data represents parameters for Diffie-Hellman key agreement
algorithm. I try to decode them by calling DH::BERDecode(). This call
is successful, but generating of common secret is failed: DH::Agree()
returns false.
I have investigate this problem. DH::BERDecode() calls the function
below. For my data this function will work strange...
void DL_GroupParameters_IntegerBased::BERDecode(BufferedTransformation
&bt)
{
BERSequenceDecoder parameters(bt);
Integer p(parameters);//First we decode Modulus. OK
Integer q(parameters);//Here we should decode Generator!!!
Integer g;//But Generator is decoded here...
if (parameters.EndReached())
{
g = q;
q = ComputeGroupOrder(p) / 2;
}
else
//In my data
Generator is equal to private key's length...
g.BERDecode(parameters);
parameters.MessageEnd();
SetModulusAndSubgroupGenerator(p/* Modulus. OK */, g/* private key's
length. BAD */);
SetSubgroupOrder(q);
}
ASN1 description of PKCS #3 structure.
DHParameter ::= SEQUENCE {
prime INTEGER, -- p
base INTEGER, -- g
privateValueLength INTEGER OPTIONAL }
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