Transport Layer Security (TLS), the successor to Secure Sockets Layer (SSL), is a protocol for secure network communication and is most frequently known trough its use in HTTPS. The goal of TLS is to achieve both integrity and confidentiality of the transmitted information between a client and a server.
TLS is initiated with a handshake, which after complete, the connection is considered secure for information exchange. Due to this TLS establishes a stateful connection.
The handshake utilizes both asymmetric and symmetric cryptography. The asymmetric keys are the public-private key-pair of the X.509v3 certificate which the server presents to the client.
By using this certificate, the client can authenticate the server. By verifying whether the certificate has been signed by a trusted Certificate Authority (CA), the trust of the CA is extended to the server. If the client also has a certificate, the server may verify the identity of the client as well in a similar manner.
Cipher suites are made up of several components:
Key Exchange Algorithm: How the symmetric keys will be exchanged
Authentication Algorithm: How the authentication of the server and optionally the client will be performed
Data Encryption Algorithm: How the symmetric key will be used to encrypt the data
Message Authentication Algorithm: How the connection will perform integrity checks
Examples of cryptographic algorithms and their use cases:
Cryptographic algorithms by type:
Symmetric Block Ciphers: DES, AES
Symmetric Stream Ciphers: ChaCha20, RC4
Asymmetric Ciphers: RSA, DSA, DH, ECDH
"A mode of operation describes how to repeatedly apply a cipher's single-block operation to securely transform amounts of data larger than a block"
AES encrypts blocks of 128-bits using a key of length 128, 192 or 256 bits while DES encrypts blocks of 64-bits. Stream ciphers on the other hand encrypt bit by bit.
"Block cipher modes of operation have been developed to eliminate the chance of encrypting identical blocks of text the same way"
Authenticated encryption (AE),
A combination of MAC and Encryption.
Authenticated Encryption with Associated Data (AEAD)
GCM and CCM
A note on insecure ciphers
Example of cipher suites: