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Xor–encrypt–xor
The xor–encrypt–xor (XEX) is a (tweakable) mode of operation of a block cipher. In tweaked-codebook mode with ciphertext stealing (XTS mode), it is one of the more popular modes of operation for whole-disk encryption. XEX is also a common form of key whitening, and part of some smart card proposals. History In 1984, to protect DES against exhaustive search attacks, Ron Rivest proposed DESX: XOR a pre- whitening key to the plaintext, encrypt the result with DES using a secret key, and then XOR a postwhitening key to the encrypted result to produce the final ciphertext.Orr Dunkelman, Nathan Keller, and Adi Shamir"Minimalism in Cryptography: The Even–Mansour Scheme Revisited" In 1991, motivated by Rivest's DESX construction, Even and Mansour proposed a much simpler scheme (the "two-key Even–Mansour scheme"), which they suggested was perhaps the simplest possible block cipher: XOR the plaintext with a prewhitening key, apply a publicly known unkeyed permutation (in pract ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Encryption Theory
Disk encryption is a special case of data 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: # they can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disk Encryption Theory
Disk encryption is a special case of data 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: # they can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
XTS Mode
Disk encryption is a special case of data at rest, 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 Hardware-based full disk encryption, disk encryption hardware. Problem definition Disk encryption methods aim to provide three distinct properties: # The data on the disk should remain confidentiality, 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 (cryptography), adversary from whom the data is being kept confidential. The s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 has to be non-repeating and, for some modes, random as well. The initialization vector is used to ensure 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 modes operat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DESX
In cryptography, DES-X (or DESX) is a variant on the DES (Data Encryption Standard) symmetric-key block cipher intended to increase the complexity of a brute-force attack using a technique called ''key whitening''. The original DES algorithm was specified in 1976 with a 56-bit key size: 256 possibilities for the key. There was criticism that an exhaustive search might be within the capabilities of large governments, particularly the United States' National Security Agency (NSA). One scheme to increase the key size of DES without substantially altering the algorithm was DES-X, proposed by Ron Rivest in May 1984. The algorithm has been included in RSA Security's BSAFE cryptographic library since the late 1980s. DES-X augments DES by XORing an extra 64 bits of key (K1) to the plaintext ''before'' applying DES, and then XORing another 64 bits of key (K2) ''after'' the encryption: \mbox(M) = K_2 \oplus \mbox_K(M \oplus K_1) The key size is thereby increased to 56 + (2 × 6 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 has to be non-repeating and, for some modes, random as well. The initialization vector is used to ensure 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 modes operat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciphertext Stealing
In cryptography, ciphertext stealing (CTS) is a general method of using a block cipher mode of operation that allows for processing of messages that are not evenly divisible into blocks without resulting in any expansion of the ciphertext, at the cost of slightly increased complexity. General characteristics Ciphertext stealing is a technique for encrypting plaintext using a block cipher, without padding the message to a multiple of the block size, so the ciphertext is the same size as the plaintext. It does this by altering processing of the last two blocks of the message. The processing of all but the last two blocks is unchanged, but a portion of the ''second''-last block's ciphertext is "stolen" to pad the last plaintext block. The padded final block is then encrypted as usual. The final ciphertext, for the last two blocks, consists of the partial penultimate block (with the "stolen" portion omitted) plus the full final block, which are the same size as the original plainte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Key Whitening
In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine the data with portions of the key. Details The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption. The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique ''whitening''. The cipher FEAL (followed by Khufu and Khafre) introduced the practice of key whitening using portions of the same key used in the rest of the cipher. This offers no additional protection from brute force attacks, but it can make other attacks more difficult. In a Feistel cipher or similar a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smart Card
A smart card, chip card, or integrated circuit card (ICC or IC card) is a physical electronic authentication device, used to control access to a resource. It is typically a plastic credit card-sized card with an embedded integrated circuit (IC) chip. Many smart cards include a pattern of metal contacts to electrically connect to the internal chip. Others are contactless smart card, contactless, and some are both. Smart cards can provide personal identification, authentication, data storage, and application processing. Applications include identification, financial, mobile phones (SIM), public transit, computer security, schools, and healthcare. Smart cards may provide strong security authentication for single sign-on (SSO) within organizations. Numerous nations have deployed smart cards throughout their populations. The universal integrated circuit card, or SIM card, is also a type of smart card. , 10.5billion smart card IC chips are manufactured annually, including 5.44billion SI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xor Encrypt Xor (XEX) Mode Encryption
Exclusive or or exclusive disjunction is a logical operation that is true if and only if its arguments differ (one is true, the other is false). It is symbolized by the prefix operator J and by the infix operators XOR ( or ), EOR, EXOR, , , , , , and . The negation of XOR is the logical biconditional, which yields true if and only if the two inputs are the same. It gains the name "exclusive or" because the meaning of "or" is ambiguous when both operands are true; the exclusive or operator ''excludes'' that case. This is sometimes thought of as "one or the other but not both". This could be written as "A or B, but not, A and B". Since it is associative, it may be considered to be an ''n''-ary operator which is true if and only if an odd number of arguments are true. That is, ''a'' XOR ''b'' XOR ... may be treated as XOR(''a'',''b'',...). Truth table The truth table of A XOR B shows that it outputs true whenever the inputs differ: Equivalences, elimination, and introduc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Key Whitening
In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine the data with portions of the key. Details The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption. The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique ''whitening''. The cipher FEAL (followed by Khufu and Khafre) introduced the practice of key whitening using portions of the same key used in the rest of the cipher. This offers no additional protection from brute force attacks, but it can make other attacks more difficult. In a Feistel cipher or similar a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orr Dunkelman
__INDEX__ Orr Dunkelman ( he, אור דונקלמן) is an Israeli cryptographer and cryptanalyst, currently a professor at the University of Haifa Computer Science department. Dunkelman is a co-director of the Center for Cyber Law & Privacy at the University of Haifa and a co-founder of Privacy Israel, an Israeli NGO for promoting privacy in Israel. Biography Dunkelman received all his degrees at the Technion - Israel Institute of Technology. He received his Ph.D. degree at the age of 25, under the supervision of Eli Biham. Before joining the University of Haifa, Dunkelman held post-doctoral positions at KU Leuven, at École normale supérieure, and at the Weizmann Institute of Science. Contributions to cryptanalysis Among his contributions to cryptanalysis are: * Dissection attack – joint work with Itai Dinur, Nathan Keller, and Adi Shamir, recipient of the Best Paper Award at the Crypto 2012 conference. * Rectangle attack – joint work with Eli Biham and Natha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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