The -salt argument actives an OpenSSL-compatible method of generating the encryption/decryption key and IV. If salt has the value "1", then a random salt is computed (highly recommended). Any other non-false value will be interpreted as the bytes of the actual salt to use. If you provide the salt, it must be exactly 8 bytes in length. It is highly recommended that you use -salt=>1, as this may become the default in future versions of this module.