Authentication intermittently fails due to incorrect padding.

[uunicorn]

Random bytes in the PW_Encode.pad() are not allowed to be zero:
See JS_RSA.js:

// PKCS#1 (type 2, random) pad input string s to n bytes, and return a bigint
function pkcs1pad2(s,n) {
...
  while(n > 2) { // random non-zero pad
    x[0] = 0;
    while(x[0] == 0) rng.nextBytes(x);
    ba[--n] = x[0];
  }
...
}