Cipher Block Chaining (CBC)

Cipher input is XOR of current plaintext block with preceding ciphertext block. For $C_0=IV$ (initialisation vector) and $1<i\le N$:

Encryption	Decryption
$\begin{array}{rl}{C}_1& =E(K,IV\oplus P_1)\\ C_i& =E(K,C_{i-1}\oplus P_i)\end{array}$	$\begin{array}{rl}{P}_1& =D(K,C_1)\oplus IV\\ P_i& =D(K,C_i)\oplus C_{i-1}\end{array}$

This requires the last block to be padded to a full $b$ bits if it is a partial block.