/** Hash one or two MPIs. To hash only one MPI, b may be set to NULL. */
public static MPI hash(int version, MPI a, MPI b, Provider prov) throws OTRException {
int totalsize = 1 + 4 + a.getLength();
if (b != null) {
totalsize += 4 + b.getLength();
}
byte[] buf = new byte[totalsize];
OutBuf obuf = new OutBuf(buf);
obuf.writeByte((byte) version);
obuf.writeUInt(a.getLength());
a.writeRaw(obuf);
if (b != null) {
obuf.writeUInt(b.getLength());
b.writeRaw(obuf);
}
byte[] out = obuf.getBytes();
SHA256 sha = prov.getSHA256();
byte[] digest = sha.hash(out);
return new MPI(digest);
}
