Block Cipher Definition

​In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called a block, with an unvarying transformation that is specified by a symmetric key. Block ciphers operate as important elementary components in the design of many cryptographic protocols, and are widely used to implement encryption of bulk data.

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Block Cipher Principles

• The stronger the encryption the hungrier the algorithm for CPU resources. However, the speed of modern processors is beginning to negate this issue
• Longer key lengths generally offer stronger encryption than short keys
• Asymmetric encryption is weaker than symmetric encryption using the same key length, but it is relatively slow.
• Block ciphers with long keys offer more strength than stream ciphers
• Passwords with long strings and unfamiliar words found in the English language are harder to crack
• When encrypting lots of data, it is best to encrypt the data using a symmetric key, and encrypt the symmetric key with an asymmetric key.
• Encrypted data cannot be compressed, but compressed data can be encrypted. If compression is used, if encryption is used, it is best to compress data before encrypting it.
• Best not use FTP
• Double encrypt, send encrypted files over an encrypted connection
• Use VPN for remote access
• Always use SSL for web access to any protected data
• If portable devices are required, then full disk encryption (file and folder level encryption)