def METHOD_NAME(cls, x):
    """Perform two rounds of ChaCha cipher"""
    for a, b, c, d in cls._round_mixup_box:
        xa = x[a]
        xb = x[b]
        xc = x[c]
        xd = x[d]
        xa = (xa + xb) & 0xffffffff
        xd = xd ^ xa
        xd = ((xd << 16) & 0xffffffff | (xd >> 16))
        xc = (xc + xd) & 0xffffffff
        xb = xb ^ xc
        xb = ((xb << 12) & 0xffffffff | (xb >> 20))
        xa = (xa + xb) & 0xffffffff
        xd = xd ^ xa
        xd = ((xd << 8) & 0xffffffff | (xd >> 24))
        xc = (xc + xd) & 0xffffffff
        xb = xb ^ xc
        xb = ((xb << 7) & 0xffffffff | (xb >> 25))
        x[a] = xa
        x[b] = xb
        x[c] = xc
        x[d] = xd