Q&A for How to Encode and Decode Using the Vigènere Cipher

Playfair uses pairs of capital letters. If you want to have lower case letters too, the alphabet of the classic ciphers could be enhanced. All modern ciphers support all kind of characters.

It's not W + L = L, but L + L = W. You take the written L, check with your keyword letter written under (L), and on your board you will find W.

Yes, for instance: (your message), and if that was z gfxr cvd (not real message) you could just go: z=a, g=t, and so on.

The cypher technique is the Caesar cipher, which substitutes letters in the alphabet.

No. RSA is a very different type of cipher from Vigenere. Cracking RSA is done by finding the prime factors of an inconveniently large number.

First you want to find the length of the unknown keyword. Do that by looking for repeated letter sequences in the ciphertext. In the likely case that they came from encrypting the same plaintext, the distance between them is a multiple of the keyword length. Once you know the length of the keyword, Vigenere reduces to a bunch of Caesar ciphers which are easily cracked by frequency analysis, etc.