Format-Preserving Cipher for Random-Access Data Encryption
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Solution Overview
Problem
Existing cipher algorithms fail to enable random-access or non-linear encryption and decryption of data, and they cannot efficiently handle multi-byte values, especially those that are non-contiguous, which is crucial for preserving the format of encrypted data in IT systems.
Innovation Solution
A format-preserving encryption and decryption method that allows selective encryption and decryption of data based on predetermined criteria, using forward and reverse mappings to ensure ciphertext values remain within specified bounds, and employing a key-stream generator like CTR mode or RC4 to iterate over input data and key-stream, skipping excluded values to maintain data format integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cipher algorithms are used to encrypt data, then encryption security is achieved, but the format of the encrypted data is lost and random access is not enabled
Solution Approach 1:
The patent applies parameter changes by modifying the encryption process to operate within constrained value ranges. The cipher algorithm transforms plaintext values within a specific range (e.g., 0-9 for numeric data) into ciphertext values that remain within the same range, rather than producing arbitrary byte values. This is achieved through modular arithmetic operations that ensure the encrypted output maintains the original data format and enables random access to encrypted records.
2Reliability
If entire datasets are encrypted to ensure security, then data protection is improved, but encryption performance deteriorates due to processing unnecessary data
Solution Approach 1:
The patent applies segmentation by dividing the encryption process into selective operations on individual data fields or records rather than encrypting entire datasets. The system identifies and encrypts only the specific sensitive fields that require protection, leaving other non-sensitive data unencrypted. This field-level or record-level segmentation approach maintains security for critical information while significantly improving encryption performance by avoiding processing of unnecessary data.
3Manufacturing precision
If format-preserving encryption is implemented, then data format integrity is maintained, but the cipher algorithm complexity increases
Solution Approach 1:
The patent resolves the complexity issue by using parameter changes through modular arithmetic with carefully selected moduli. The encryption algorithm uses simple operations (addition, subtraction, multiplication) modulo a value that corresponds to the size of the allowed character set or value range. This approach maintains format integrity while keeping the algorithm relatively simple and efficient, avoiding the need for complex custom cryptographic constructions.
Data Source
AI summary
A format-preserving cipher including an encryption and a decryption scheme supporting non-linear access to input data by allowing the selection of portions of data from a potentially larger dataset to be encrypted, thus avoiding a necessarily sequential access into the input plaintext data. The cipher first defines a forward mapping from the allowable ciphertext values to an integer set of the number of such allowable ciphertext values, and a corresponding reverse mapping. It also supports exclusion of a certain set of characters from the ciphering process. Further, the encryption algorithm can encrypt the input plaintext data while preserving its original format and length and a corresponding decryption algorithm. The cipher advantageously embodies the encryption and decryption of multi-byte values or strings of data, thus fitting a variety of industrial needs.