Today I went to my internship. I made a polyalphabetic cipher. In a polyalphabetic cipher each character is shifted by a different Caeser Cipher. The Caeser Cipher used for each character is based on a key.  This prevents people from doing frequency analysis on the encrypted messages.

Polyalphabetic Cipher

I also learned about One Time Pad, which is the only encryption that cannot be decrypted. The way it works is that it first converts the message into bits (one's and zero's) and then does exclusive or with a randomly generated key. Exclusive or compares the message to the key and if the numbers are same at that position they place a zero and if they are different they place a one. The reason this is hard to decrypt is because the key is randomly generated every time. A rule with One Time Pad is that you can only use a key one time or the message will be decryptable. Another interesting thing I learned about is homomorphic cryptography. Homomorphic cryptography allows you to send an encrypted message to a company or another person, who can then manipulate the data/message without ever decrypting it. Then after they manipulate it, they can send it back to the original person who can then decrypt the manipulated data.