Encryption is scrambling data so others cannot view it unless they know what method you used to encrypt it and what key you used.
Decryption is turning this scrambled data back into plaintext.
Plaintext is a human-readable form of data.
Ciphertext is encrypted data.
Encryption is used in a lot of scenarios:
This is named after a Roman emporer, and is where letters are shifted a set number of places left / right by a certain number of places to encrypt, then to decrypt they are simply shifted in the opposite direction. This can easily be cracked using frequency analysis or brute force.
This was invented to enforce data security between telex machines during World War 1. This is known as a one-time pad as the key used to encrypt / decrypt a message is discarded after one use. This is completely mathematically secure and is to this day unbreakable. This uses a random sequence of letters and symbols with a length at least the length of the text to encrypt, that must be truly random. Because the sender and receiver both need the key to encrypt / decrypt data.
The algorithm is as follows for each character (where X is the character, K is the key, and Y is the result):
To decrypt:
## Frequency analysis This only works for substitution ciphers, and is where you record how many times each letter occurs in the encrypted text, then use this to make educated guesses on what each letter corresponds to based on their frequency in English in general. It’s basically computer hangman. The letter ‘e’ appears most frequently in English according to a number of records.
This is where you encrypt every possible combination of text in order to find the one that is the same as the encrypted value you want to decrypt. This takes a very long time as it runs for so long.