ANSI X9.124-1 pdf free download
ANSI X9.124-1 pdf free download.Symmetric Key Cryptography for the Financial Services Industry一 Format-Preserving Encryption- Part 1: Definitions and Model.
4.15 EBCDIC
The Extended Binary Coded Decimal Interchange Code is a scheme for mapping characters to byte values. EBCDIC defines different mappings than the ASCII scheme, and comprises multiple code pages containing different sets of characters. EBCDIC is mostly an 8-bit scheme, although it includes double-byte extensions.
4.16 Feistel network
A Feistel network is a cryptographic structure that uses multiple pseudorandom functions (PRFs) in a series of iterated rounds to form a block cipher. Each round consists of applying a PRF to half the input and combining the PRF output with the other half of input using a simple operation, such as XQR.
4.17 FFX
The FFX mode is a family of format-preserving ciphers. FFX stands for Format-preserving, Feistel-based, where the X reflects a specific algorithm.
4.18 format
A format consists of a length and a set of characters. It describes a set of character strings that are exactly
that length and only consist of characters from the set. As an example, the string “1101225283369474” belongs tothe format with length 16 and character set {0,…,9}.
4.19 formatted string
A formatted string is a series of characters that conform to some given format.
4.20 FPE (Format-Preserving Encryption)
Format-Preserving Encryption is the process of encrypting a formatted string with a block cipher or stream cipher using a mode such that the resultant ciphertext conforms to the same format as the plaintext.
4.21 malleability
Malleability is the ability of an attacker to induce predictable changes in the plaintext by changing the ciphertext.
4.22 mode (block cipher mode of operation)
A mode is an algorithm for processing data with a block cipher so as to achieve some defined security property.Examples include CBC (Cipher Block Chaining) mode and CTR (Counter) mode.
5 Format.Preserving Encryption (FPE)
5.1 Techniques
Format-Preserving Encryption techniques aim to encrypt strings with some given format (for example, credit card PANs, which are formatted as 12-19-digit numeric values) in such a way that the resultant ciphertext keeps that same format. These techniques enable placing encrypted data into applications, protocols and databases with minimal alteration to existing data structures. As an example, a Point-Of-Sale terminal might encrypt credit card data using FPE and insert that encrypted data into an existing authorization message field, and intermediate applications can transport the data without modification to support a larger field. A number of other standards (e.g., ANSI X9.119-1) define methods for employing FPE to secure financial data.
FPE techniques as defined by this standard fall into two classes:
Block ciphers, where a key is used to generate a random 1:1 mapping over the space of all strings in a given format. The ANSI X9.124 part 3, 4, and 5 documents define methods for building format-preserving block ciphers using TDEA (part 5) and AES (part 3, 4 and 5) as the underlying cryptographic primitive.
Stream ciphers, where a key is used to generate a stream of random offsets that are combined with each character of the plaintext, typically using an exclusive-or (XQR) operation. These techniques are useful when the underlying encryption key can be changed on each encryption operation, and some application mechanism defends against maliciously altered plaintext. The ANSI X9. 124 part 2 document defines an AES counter mode technique for building a format-preserving stream cipher.
This Standard supplies a set of definitions common to all these techniques, a security model for FPE block cipher techniques, and a pseudocode language used in the later parts to define the exact FPE algorithms.
ANSI X9.124-1 pdf download.
