Basically we need a method where we provide the message and the key, and then we loop through the message and xor it with the key.For this particular example, I will be working on Wndows (sorry X users). I wrote this one in the conventional method and my attempt at linq, to compare what was easiest for me to read and what was fastest. Encryption algorithmīefore explaining how we get hold of the key, I just want to cover the necessary code for encryption/decryption of the text as well as the main method, and let us start out with the encryption method. I tried to dive a bit into linq for this purpose, since it involves juggling multiple arrays around a lot, and I thought it might be easier to solve parts of it with linq. All digits are lower case English letters.However, wWe know quite a lot about the encrypted message, but lets just have a short list of what we actually know about the encrypted text. We could brute force through all the keys since there are only 26 3 = 17576. Using cipher1.txt (right click and ‘Save Link/Target As…’), a file containing the encrypted ASCII codes, and the knowledge that the plain text must contain common English words, decrypt the message and find the sum of the ASCII values in the original text. Your task has been made easy, as the encryption key consists of three lower case characters. The balance for this method is using a sufficiently long password key for security, but short enough to be memorable. If the password is shorter than the message, which is likely, the key is repeated cyclically throughout the message. Unfortunately, this method is impractical for most users, so the modified method is to use a password as a key. The user would keep the encrypted message and the encryption key in different locations, and without both “halves”, it is impossible to decrypt the message. The advantage with the XOR function is that using the same encryption key on the cipher text, restores the plain text for example, 65 XOR 42 = 107, then 107 XOR 42 = 65.įor unbreakable encryption, the key is the same length as the plain text message, and the key is made up of random bytes. For example, uppercase A = 65, asterisk (*) = 42, and lowercase k = 107.Ī modern encryption method is to take a text file, convert the bytes to ASCII, then XOR each byte with a given value, taken from a secret key. The problems reads:Įach character on a computer is assigned a unique code and the preferred standard is ASCII (American Standard Code for Information Interchange). I had much fun trying to crack the code of this problem. Problem 59 of Project Euler is about encryption, and modern days encryption relies heavily on mathematics. People who know me would also know how much I have been looking forward to this exercise.
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