Encrypting with Vigenere procedure without a key

Question

I'm learning about Vigenere cipher,and I came across an exercise asking to encrypt a plain text without a key.

How would that work exactly?

Answer 1

Guess what! There is actually a way to encrypt Vigenére without a key, assuming that you are using the Vigenére Square. Simple use the english alphabet as the key (repeat as necessary).

Example:

MYSECRETMESSAGEWHICHYOUPROBABLYCANFINDANYWAY ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQR

Now just use the Vigenére Square to replace the message letters with whatever corresponds to row/column.

Hope this helps.

Answer 2

There is no such thing as Vigenère encryption "without a key".

Whoever asked you to do such a thing is either deeply confused or is using an utterly nonstandard and idiosyncratic meaning of the word "Vigenère". In the latter case you have to ask them what they mean by it. Random people on the internet will not be able to read their mind remotely for you.