Net215:Basic_Crypto_HTTPS_and_TLS - ConnorEast/Tech-Journal GitHub Wiki

Terminology

Cryptography: "lock and key", protects data by disguising it as something else
Cipher: Method to disguise text
PlainText: the original text
CipherText: the disguised text
Encrypt: the process of disguising
Decrypt: removes the disguise
Algorithm: Step-by-step procedure for calculations
Key: A piece of information which determines the functional output of a cryptographic algorithm or cipher
Hash function: an algorithm that takes an arbitrary block of data and returns a fixed-size bit string
Message Digest: Result of a hash function

Cryptography and computing

Confidentiality: Using Cryptography to keep data private
Integrity: Crypto to ensure that data has not been altered
Authentication: Verify that user is who they claim to be
Non-Repudiation: Ensure that user performed a specific activity

Confidentiality and Crypto

There are two common applications of encryption: encryption in transit & Encryption at rest. The major methods used would be either Symmetric or Asymmetric encryption. Symmetric being where the data is encrypted using the other devices public keys. Asymmetric encryption would be where the data is encrypted based on the opposite devices private keys.

In some cases both symmetric and asymmetric keys are used in tandem.

Asymetric Encryption	Symmetric Encryption
Uses "key pairs": Public Key + Private Key Devices encrypted using the public key can only be decrypted by the matching private key Any message encrypted using the private key can only be decrypted by the matching private key *Pros:* Easy key exchange! *Cons:* Slower, more complex	A secret key (alphanumeric string) is applied to a message to change the content The same key is used to encrypt/decrypt messages *Pros:* Simple/Fast/Effective. *Cons:* Exchanging the private key is challenging.

TLS (Transport Layer Security)

Designed to secure network traffic
Layer 6 Protocol [Some people say its layer 5]

Relies on both Symmetric and asymmetric encryption

Uses asymmetric encryption to exchange a symmetric key
Uses symmetric encryption to encrypt the rest of the communication

How TLS Works

>Step 1: Completion of 3-way handshake [Syn/Syn-ACK/ACK]

>Step 2: Client Hello is sent containing TLS supported version. A session ID is set, and a random number for encryption is sent

>Step 3: Server Hello is sent containing the TLS version to use to connect. A second random number is generated for symmetric encryption

>Step 4: Server sends a digital certificate containing its public key

>Step 5: Server sends a Server Hello Done message

>Step 6: Client sends a pre-master secret to the server. The server than generates the master key which is used for symmetric encryption.

>Step 7: Client sends a handshake finished message. The server sends a handshake finished message. Encryption is now functional

TLS Non-Protected Information

IP Addresses of Client and Server
Ports of Client and Server
Relative size of files/sites
DNS requests made to connect to the server