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Block Cipher Modes Of Operation
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. 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. 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. Most modes require a unique binary sequence, often called an initialization vector (IV), for each encryption operation. The IV must be non-repeating, and for some modes must also be random. The initialization vector is used to ensure that distinct ciphertexts are produced even when the same plaintext is encrypted multiple times independently with the same key. Block ciphers may be capable of operating on more than one block size, but during transformation the block size is always fixed. Block cipher mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Encryption Theory
Disk encryption is a special case of data at rest protection when the storage medium is a sector-addressable device (e.g., a hard disk). This article presents cryptographic aspects of the problem. For an overview, see disk encryption. For discussion of different software packages and hardware devices devoted to this problem, see disk encryption software and disk encryption hardware. Problem definition Disk encryption methods aim to provide three distinct properties: # The data on the disk should remain confidential. # Data retrieval and storage should both be fast operations, no matter where on the disk the data is stored. # The encryption method should not waste disk space (i.e., the amount of storage used for encrypted data should not be significantly larger than the size of plaintext). The first property requires defining an adversary from whom the data is being kept confidential. The strongest adversaries studied in the field of disk encryption have these abilities: # th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OCB Mode
Offset codebook mode (OCB mode) is an authenticated encryption mode of operation for cryptographic block ciphers. OCB mode was designed by Phillip Rogaway, who credits Mihir Bellare, John Black, and Ted Krovetz with assistance and comments on the designs. It is based on the '' integrity-aware parallelizeable mode'' (IAPM) of authenticated encryption by Charanjit S. Jutla. The ''OCB2'' version was proven insecure, while the original ''OCB1'' as well as ''OCB3'' from 2011 are still considered secure. Encryption and authentication OCB mode was designed to provide both message authentication and privacy. It is essentially a scheme for integrating a message authentication code (MAC) into the operation of a block cipher. In this way, OCB mode avoids the need to use two systems: a MAC for authentication and encryption for confidentiality. This results in lower computational cost compared to using separate encryption and authentication functions. There are three versions of OC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IAPM (mode)
Integrity-aware parallelizable mode (IAPM) is a mode of operation for cryptographic block ciphers. As its name implies, it allows for a parallel mode of operation for higher throughput. Encryption and authentication At the time of its creation, IAPM was one of the first cipher modes to provide both authentication and privacy in a single pass. (In earlier authenticated encryption designs, two passes would be required to: one to encrypt, and the second to compute a MAC.) IAPM was proposed for use in IPsec. Other AEAD schemes also provide all of the single pass, privacy and authentication properties. IAPM has mostly been supplanted by Galois/counter mode. See also * OCB mode Offset codebook mode (OCB mode) is an authenticated encryption mode of operation for cryptographic block ciphers. OCB mode was designed by Phillip Rogaway, who credits Mihir Bellare, John Black, and Ted Krovetz with assistance and comments o ... IAPM modedescribed in more detail in Hebrew Wik ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EAX Mode
EAX mode (encrypt-then-authenticate-then-translate) is a mode of operation for cryptographic block ciphers. It is an Authenticated Encryption with Associated Data ( AEAD) algorithm designed to simultaneously provide both authentication and privacy Privacy (, ) is the ability of an individual or group to seclude themselves or information about themselves, and thereby express themselves selectively. The domain of privacy partially overlaps with security, which can include the concepts of a ... of the message ( authenticated encryption) with a two-pass scheme, one pass for achieving privacy and one for authenticity for each block. EAX mode was submitted on October 3, 2003, to the attention of NIST in order to replace CCM as standard AEAD mode of operation, since CCM mode lacks some desirable attributes of EAX and is more complex. Encryption and authentication EAX is a flexible nonce-using two-pass AEAD scheme with no restrictions on block cipher primitive to be used, nor o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CWC Mode
In cryptography, CWC Mode (Carter–Wegman + CTR mode) is an AEAD block cipher mode of operation that provides both encryption and built-in message integrity, similar to CCM and OCB modes. It combines the use of CTR mode with a 128-bit block cipher for encryption with an efficient polynomial Carter–Wegman MAC with a tag length of at most 128 bits and is designed by Tadayoshi Kohno, John Viega and Doug Whiting. CWC mode was submitted to NIST The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ... for standardization, but NIST opted for the similar GCM mode instead. Although GCM has weaknesses compared to CWC, the GCM authors successfully argued for GCM. CWC allows the payload and associated data to be at most 232 - 1 blocks or nearly 550 GB. References External links CWC mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CCM Mode
CCM mode (counter with cipher block chaining message authentication code; counter with CBC-MAC) is a mode of operation for cryptographic block ciphers. It is an authenticated encryption algorithm designed to provide both authentication and confidentiality. CCM mode is only defined for block ciphers with a block length of 128 bits. The nonce of CCM must be carefully chosen to never be used more than once for a given key. This is because CCM is a derivation of counter (CTR) mode and the latter is effectively a stream cipher. Encryption and authentication As the name suggests, CCM mode combines counter (CTR) mode for confidentiality with cipher block chaining message authentication code (CBC-MAC) for authentication. These two primitives are applied in an "authenticate-then-encrypt" manner: CBC-MAC is first computed on the message to obtain a message authentication code (MAC), then the message and the MAC are encrypted using counter mode. The main insight is that the same ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galois/Counter Mode
In cryptography, Galois/Counter Mode (GCM) is a mode of operation for symmetric-key cryptographic block ciphers which is widely adopted for its performance. GCM throughput rates for state-of-the-art, high-speed communication channels can be achieved with inexpensive hardware resources. The GCM algorithm provides both data authenticity (integrity) and confidentiality and belongs to the class of authenticated encryption with associated data (AEAD) methods. This means that as input it takes a key K, some plaintext P, and some associated data AD; it then encrypts the plaintext using the key to produce ciphertext C, and computes an authentication tag T from the ciphertext and the associated data (which remains unencrypted). A recipient with knowledge of K, upon reception of AD, C and T, can decrypt the ciphertext to recover the plaintext P and can check the tag T to ensure that neither ciphertext nor associated data were tampered with. GCM uses a block cipher with block size 128 bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HMAC
In cryptography, an HMAC (sometimes expanded as either keyed-hash message authentication code or hash-based message authentication code) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key. As with any MAC, it may be used to simultaneously verify both the data integrity and authenticity of a message. An HMAC is a type of keyed hash function that can also be used in a key derivation scheme or a key stretching scheme. HMAC can provide authentication using a shared secret instead of using digital signatures with asymmetric cryptography. It trades off the need for a complex public key infrastructure by delegating the key exchange to the communicating parties, who are responsible for establishing and using a trusted channel to agree on the key prior to communication. Details Any cryptographic hash function, such as SHA-2 or SHA-3, may be used in the calculation of an HMAC; the resulting MAC algori ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CBC-MAC
In cryptography, a cipher block chaining message authentication code (CBC-MAC) is a technique for constructing a message authentication code (MAC) from a block cipher. The message is encrypted with some block cipher algorithm in cipher block chaining (CBC) mode to create a chain of blocks such that each block depends on the proper encryption of the previous block. This interdependence ensures that a change to any of the plaintext bits will cause the final encrypted block to change in a way that cannot be predicted or counteracted without knowing the key to the block cipher. To calculate the CBC-MAC of message , one encrypts in CBC mode with zero initialization vector and keeps the last block. The following figure sketches the computation of the CBC-MAC of a message comprising blocks m_1\, m_2\, \cdots\, m_x using a secret key and a block cipher : CBC-MAC on its own is not secure for variable-length messages (see the discussion below) and is currently used to construct a pse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
