Return a list of the bit indexes that the "key tweak" applies to,
    as determined by the FLASH_CRYPT_CONFIG 4 bit efuse value.

def _flash_encryption_tweak_range(flash_crypt_config=0xF):
    """ Return a list of the bit indexes that the "key tweak" applies to,
    as determined by the FLASH_CRYPT_CONFIG 4 bit efuse value.
    """
    tweak_range = []
    if (flash_crypt_config & 1) != 0:
        tweak_range += range(67)
    if (flash_crypt_config & 2) != 0:
        tweak_range += range(67, 132)
    if (flash_crypt_config & 4) != 0:
        tweak_range += range(132, 195)
    if (flash_crypt_config & 8) != 0:
        tweak_range += range(195, 256)
    return tweak_range