static int GetRSAPublicKeySize(byte[] kv)
{
AsnElt ae = AsnElt.Decode(kv);
ae.CheckTag(AsnElt.SEQUENCE);
ae.CheckNumSub(2);
AsnElt ai = ae.GetSub(0);
ai.CheckTag(AsnElt.INTEGER);
ai.CheckPrimitive();
byte[] v = ai.CopyValue();
if (v.Length > 0 && v[0] >= 0x80)
{
throw new AsnException(
"Invalid RSA modulus (negative)");
}
int bitLen = M.BitLength(v);
if (bitLen < 512)
{
throw new AsnException(string.Format(
"Invalid RSA modulus ({0} bits)", bitLen));
}
else if ((v[v.Length - 1] & 0x01) == 0)
{
throw new AsnException("Invalid RSA modulus (even)");
}
return(bitLen);
}
