code: function (a, bstart, bend) {
      a = sjcl.bitArray._shiftRight(a.slice(bstart/32), 32 - (bstart & 31)).slice(1);
      return (bend === undefined) ? a : sjcl.bitArray.clamp(a, bend-bstart);
    }
docs: Array slices in units of bits.
  @param {bitArray} a The array to slice.
  @param {Number} bstart The offset to the start of the slice, in bits.
  @param {Number} bend The offset to the end of the slice, in bits.  If this is undefined,
  slice until the end of the array.
  @return {bitArray} The requested slice.