Method Crypto.Substitution()->set_key()

Method set_key: this_program set_key(mapping(string:string|array(string)) key)
Description: Sets the encryption and decryption key. The decryption key is derived from the encryption key by reversing the mapping. If one index maps to an array of strings, one element from the array will be chosen at random in such substitution.
Throws: An error is thrown if the encryption key can not be made reversible.