Extended Ciphertext Key Reference Embedding
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Solution Overview
Problem
Cryptographic systems face challenges in determining the encryption key used for ciphertext decryption, especially when the character domain of the ciphertext cannot be expanded beyond that of the plaintext, limiting the number of supported encryption keys.
Innovation Solution
Incorporating a key reference into the ciphertext by using a format-preserving encryptor and a key reference embedder to add a set of characters representing the key, ensuring the key reference can be determined without expanding the character domain, allowing for key rollover in systems that cannot process characters outside a specific domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a key reference is embedded into the ciphertext by expanding the character domain, then the decrypting device can determine which key was used to generate the ciphertext, but the system cannot process characters outside a specific domain (e.g., printable ASCII characters)
Solution Approach 1:
The patent embeds the key reference in a different dimension - using positional information within the existing character domain rather than expanding to new characters. The key reference is encoded by selecting specific characters at specific positions from the plaintext, creating a layered structure where the surface level maintains character domain compatibility while the embedded layer carries key identification information.
Solution Approach 2:
The key reference is nested within the ciphertext structure itself. Rather than adding external metadata, the patent embeds the key reference as an integral part of the ciphertext by selecting and positioning specific characters from the original plaintext, creating a self-contained structure that carries both encrypted data and key identification information.
2Adaptability or versatility
If the character domain of the ciphertext is expanded to embed a key reference, then sufficient encryption keys can be supported, but the system cannot display or process ciphertexts having characters outside the printable ASCII domain
Solution Approach 1:
The patent changes the parameter of key identification from character value expansion to positional encoding. Instead of using additional character space to represent keys, the system uses the position and selection of existing characters within the printable ASCII domain to encode key reference information, maintaining ease of operation while supporting multiple keys.
3Reliability
If external data such as timestamps or database columns are used to determine the encryption key, then key identification can be achieved, but the approach is often unreliable or technologically challenging
Solution Approach 1:
The patent extracts the key reference information directly from the plaintext and embeds it within the ciphertext structure, eliminating the need for external data sources like timestamps or database columns. This self-contained approach reduces system complexity by removing external dependencies while maintaining reliable key identification through the embedded character positions.
Data Source
AI summary
Examples discussed herein disclose, among other things, an encrypting device. The encrypting device may include a format preserving encryptor to obtain a plaintext, obtain a key from a plurality of keys stored in a key database, and encrypt the plaintext using the key to produce a ciphertext having a length of the plaintext. The encrypting device may also include a key reference embedder to obtain a key reference associated with the key, and generate an extended ciphertext by adding to the ciphertext a set of characters associated with the key reference, such that the key reference can be determined based on the extended ciphertext.