Block cipher algorithms encrypt data in block units, rather than a single bit at a time. The most common block size is 64 bits.
Because each block is heavily processed, block ciphers are considered more secure than stream ciphers. However, block cipher algorithms tend to execute quite a bit slower than stream ciphers.
All that the basic block encryption algorithm specifies is how to get a block of ciphertext from a block of plaintext and vice versa. All the other implementation details (for example, padding, initialization vectors, and cipher modes) are specified independently of the algorithm. These options are discussed in the next few sections.
The only block cipher provided with the Microsoft Base Cryptographic Provider is the RC2 block cipher. This algorithm has a block size of 64 bits.