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- Electronic Code Book (ECB) – Electronic code book is the easiest block cipher mode of functioning. It is easier because of direct encryption of each block of input plaintext and output is in form of blocks of encrypted ciphertext.
- Cipher Block Chaining – Cipher block chaining or CBC is an advancement made on ECB since ECB compromises some security requirements. In CBC, previous cipher block is given as input to next encryption algorithm after XOR with original plaintext block.
- Cipher Feedback Mode (CFB) – In this mode the cipher is given as feedback to the next block of encryption with some new specifications: first an initial vector IV is used for first encryption and output bits are divided as set of sandb-sbits the left hand side sbits are selected and are applied an XOR operation with plaintext bits.
- Output Feedback Mode – The output feedback mode follows nearly same process as the Cipher Feedback mode except that it sends the encrypted output as feedback instead of the actual cipher which is XOR output.
- Block Size
- Padding in Block Cipher
- Block Cipher Schemes
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Though any size of block is acceptable, following aspects are borne in mind while selecting a size of a block. 1. Avoid very small block size − Say a block size is m bits. Then the possible plaintext bits combinations are then 2m. If the attacker discovers the plain text blocks corresponding to some previously sent ciphertext blocks, then the attac...
Block ciphers process blocks of fixed sizes (say 64 bits). The length of plaintexts is mostly not a multiple of the block size. For example, a 150-bit plaintext provides two blocks of 64 bits each with third block of balance 22 bits. The last block of bits needs to be padded up with redundant information so that the length of the final block equal ...
There is a vast number of block ciphers schemes that are in use. Many of them are publically known. Most popular and prominent block ciphers are listed below. 1. Digital Encryption Standard (DES)− The popular block cipher of the 1990s. It is now considered as a ‘broken’ block cipher, due primarily to its small key size. 2. Triple DES− It is a varia...
Learn the basic scheme, block size, padding and popular schemes of block ciphers in cryptography. Compare DES, AES, IDEA and other block ciphers with their advantages and disadvantages.
Block ciphers are the elementary building blocks of many cryptographic protocols. They are ubiquitous in the storage and exchange of data, where such data is secured and authenticated via encryption. A block cipher uses blocks as an unvarying transformation.
- Electronic Feedback Mode. This is considered to be the easiest block cipher mode of operation. In electronic codebook mode (ECB) the plain text is divided into the blocks, each of 64-bit.
- Cipher Block Chaining Mode. To overcome the limitation of ECB i.e. the repeating block in plain text produces the same ciphertext, a new technique was required which is Cipher Block Chaining (CBC) Mode.
- Cipher Feedback Mode. All applications may not be designed to operate on the blocks of data, some may be character or bit-oriented. Cipher feedback mode is used to operate on smaller units than blocks.
- Output Feedback Mode. The output feedback (OFB) mode is almost similar to the CFB. The difference between CFB and OFB is that unlike CFB, in OFB the encrypted IV is fed to the encryption of next plain text block.
Learn what a block cipher is, how it works, and what modes and components it uses. See an example of a block cipher called the "Number Shifter" and how to encrypt and decrypt messages with it.
In cryptography, a block cipher mode of operation is an algorithm that uses a block cipher to provide information security such as confidentiality or authenticity. [1] . A block cipher by itself is only suitable for the secure cryptographic transformation (encryption or decryption) of one fixed-length group of bits called a block. [2] .
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Jun 3, 2021 · Learn what a block cipher is, how it works, and why it is used in cryptography. Compare block ciphers with stream ciphers and explore the common modes of block ciphers with examples.
