Encryption

Basics • Plaintext - the original message ABCDEFG • Ciphertext - the coded message DFDFSDFSD • Cipher - algorithm for transforming plaintext to ciphertext • key - info used in cipher known only to sender/receiver • Cryptanalysis (codebreaking) - the study of principles/ methods of deciphering ciphertext without knowing key • Cryptology - the field of both cryptography and cryptanalysis

More Terminology • Symmetric Encryption– Both Sender/Receiver use the same algorithms/keys for encryption/decryption • Asymmetric Encryption – Sender/receiver can employ different keys

Wireless pre-shared key [wpa-psk] Key shared between router and your devices Internet/network packets encrypted Will need a new wpa-psk ‘secret key’

How does public-key encryption work? Each person has two keys, one called a public key and one called a secret key. Each "key" is actually a long, meaningless string of numbers The public key is something you can share with anyone, while the secret key is something you must keep private

How to send a message with public-key encryption Annie wants to send a secure message to Bob First, each of them has to generate public and secret (private) keys with their computer. They need to do this only once. After they've generated a public and secret key pair, they can use it to communicate with any number of different people.

2. Swap public keys Next they swap their public keys. They keep their secret keys to themselves and never share them with anyone else. They can send their public keys to whoever they wish—it's okay even to publish your public key on your website or attach it to your emails.

3. Exchange messages To send Bob a message, Annie uses Bob's public key to encrypt her words. The encrypted message is complete gibberish and it doesn't matter who sees it. When Bob receives the message, he uses his secret key to decrypt it (turn it back into a message he can read). If he wants to reply securely to Annie, he simply runs the process in reverse: he uses Annie's public key to encrypt his message and she uses her secret key to decrypt it.

4. Digitally signing messages Bob and Annie can also use their keys to prove messages they send really come from them by adding what's called a digital signature. Bob can add a digital signature to his emails using his secret key. When Annie receives a signed message from someone claiming to be Bob, she can use his public key to prove that the message really did come from him

Different public key methods RSA (named for Ron Rivest, Adi Shamir, and Leonard Adleman), Data Encryption Standard (DES) Triple-DES Advanced Encryption Standard (AES) Hashing

DES (cracked in 1999 within 24hrs) DES stands for Digital Encryption Standard. created 1975 by NSA. DES uses a block cipher that uses a 56-bit key to create the key table. it goes through the process of combining a key from the key table with the block of plain text. after the key and the plaintext have been combined, DES goes through 16 more changes [called rounds] to mix up the cipher text. to decrypt it has to do the same in reverse.

Triple DES this is the replacement for DES. changed the algorithm. same as DES but three times more than normal DES. this uses 3 keys on each block of plain text, instead of using 1 56bit key. 3des encrypts plain text with 1 key; encrypts cipher with another 56bit key, then encrypts cipher with another 56bit key . bit of an overkill but works. common key length is 112 or 168 bits. to crack this you need to figure out 3 separate keys, enteredin the correct order

AES AES stands for Advanced Encryption Standard. The heir to DES Late in 2000, NIST announced it had a winner. Competition ran from 1997 relatively new, there is some distrust and a feeling that it has not been tested enough for weaknesses

HASHING some algorithms are used to encrypt data, but not to decrypt them The most commonly used hashes are SHA-1 (pronounced shaw-one) and MD5 Hashes take a message and pad it a bit by adding some extra data to the message. Hashes are used to prove that the data that has been transmitted is same as the original data and that nothing has been changed en route every time you use a hash algorithm on the same data, you’ll get exactly the same result. On the other hand, if the data has been changed, even by one letter or a single space, the hash will change

RSA asymmetric algorithm RSA comes from the last names of the inventors, Ron Rivest, Adi Shamir, and Leonard Adleman, who created the algorithm in 1978. To date, it is the only asymmetric algorithm in widespread general use that is used for private/public key generation and encryption. RSA uses prime numbers to create each of the keys (private & public), but using those keys to encrypt a large amount of data is impractical due to the amount of time it takes a computer to process the encryption