On 9/7/2018 9:34 AM, Xuelei Fan wrote:
JSSE should use the 'x25519' name (via NamedParameterSpec object) only.
This is the part that I don't know how to do. In JSSE, we convert
between the array containing the encoded public key and the BigInteger
representation of the public key used in XECPublicKeySpec. To do this,
you need to know the length of the key, in bits. That means that JSSE
needs to know the length of the key, in addition to the name, in order
to do this conversion. I understand that there are lots of ways to get
this information in JSSE, but I don't know which ways you would find
acceptable.
We keep going back and forth, saying the exact same things, and we don't
seem to be making any progress. Can you please provide some code to
illustrate what you want me to do? All I need is an acceptable
implementation of the following method, that is used by JSSE to decode
public keys:
public static XECPublicKeySpec decodeXecPublicKey(byte[] key,
NamedParameterSpec spec)
throws InvalidParameterSpecException {
XECParameters params = XECParameters.get(
InvalidParameterSpecException::new, spec);
BigInteger u = decodeXecPublicKey(key, params.getBits());
return new XECPublicKeySpec(spec, u);
}
For reference, here is the implementation of the helper method that does
the actual decoding, using the length.
public static BigInteger decodeXecPublicKey(byte[] key,
int bits) {
ArrayUtil.reverse(key);
// clear the extra bits
int bitsMod8 = bits % 8;
if (bitsMod8 != 0) {
int mask = (1 << bitsMod8) - 1;
key[0] &= mask;
}
return new BigInteger(1, key);
}
