iPhone app Crypto: Cæsar and Vigenère ciphers

Dive into cryptography with Crypto.
Use Caesar and Vigenre ciphers and encrypt and decrypt messages.

CRYPTO

Crypto allows you to encrypt and decrypt messages using Caesar and Vigenre ciphers.
Create a message, select a key or a keyword, and then send the encrypted message to your friends.
Similarly can you decrypt encrypted messages.

CIPHERS

In both Caesar and Vigenre ciphers, each letter is substituted with another, which makes them substitution ciphers.
Only those who know the secret key are able to decrypt messages, though it is possible to decrypt an encrypted message without knowing the key by using brute force.

CAESAR CIPHER

In the case of Caesars cipher, we use a secret integral key (k).
This secret key is used to rotate (i.e.
shift) each letter by k places, wrapping A to Z and a to z as needed.
For example, if we use the key of 1 to encrypt Hello world!, we will get Ifmmp xpsme! To decrypt this message, shift the letters backward.

VIGENRE CIPHER

Vigenre cipher improves upon Caesar cipher by shifting letters using different keys.
This sequence of keys is known as a keyword.
Each letter in the keyword represents by how far the corresponding letter in the original message will be shifted (A and a represent 0, B and b represent 1, Z and z represent 25).
If we encrypt Hello world! with the keyword Squirrel, we will get Zuftf nscdt!,

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