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Appendix 13 · New Encryption Methods for QKD and RKD

From the book: Data Encryption at the Intersection of Mathematics and Physics – Comparing Physical Methods of Cryptography

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Content of this appendix

Appendix 13 · New Encryption Methods for QKD and RKD

This appendix expands the book's discussion of encryption methods for QKD and RKD. It starts from the strict one-time-pad requirements: truly random key bits, key length at least as large as the plaintext, and no reuse. It then explains why these requirements quickly become difficult when QKD or RKD key rates are limited.

The appendix presents several modes designed to reduce the practical pressure on key volume. These methods use cyclic buffers, counters, hash functions such as HKDF or SHAKE256, and XOR operations to derive encryption material for data blocks. They are tailored to QKD and RKD because these technologies already rely on XOR and hashing in related processing steps.

The material is careful about the security trade-off. The pure one-time pad remains the reference point for provable confidentiality, while the presented modes are practical alternatives for cases where enough fresh key material cannot be generated or distributed. The appendix is therefore relevant for realistic deployments where key rate is the bottleneck.

  • Explains one-time-pad key-length constraints
  • Presents XOR-based modes for QKD and RKD
  • Uses cyclic buffers, counters, and hash functions
  • Addresses practical limits of physical key rates
  • Distinguishes ideal OTP security from usable variants

Suggested citation

Reference in IEEE style

E. Piller and H. Schölnast, “Appendix 13: New Encryption Methods for QKD and RKD,” author-maintained supplementary material for Data Encryption at the Intersection of Mathematics and Physics: Comparing Physical Methods of Cryptography, 2026. [Online]. Available: https://cryptography.study/phys/modes/.

Reference in ACM style

Ernst Piller and Hubert Schölnast. 2026. Appendix 13: New Encryption Methods for QKD and RKD. Author-maintained supplementary material for Data Encryption at the Intersection of Mathematics and Physics: Comparing Physical Methods of Cryptography. https://cryptography.study/phys/modes/

BibTeX entry 
@misc{piller_schoelnast_2026_appendix_13_encryption_modes,
  title        = {New Encryption Methods for QKD and RKD},
  author       = {Ernst Piller and Hubert Schölnast},
  year         = {2026},
  howpublished = {Author-maintained supplementary material for Data Encryption at the Intersection of Mathematics and Physics},
  url          = {https://cryptography.study/phys/modes/},
  note         = {Related book DOI: 10.1007/978-3-032-24764-3},
  language     = {en}
}
RIS entry 
TY  - GEN
TI  - New Encryption Methods for QKD and RKD
T2  - Author-maintained supplementary material for Data Encryption at the Intersection of Mathematics and Physics
AU  - Piller, Ernst
AU  - Schölnast, Hubert
PY  - 2026
UR  - https://cryptography.study/phys/modes/
N1  - Related book DOI: 10.1007/978-3-032-24764-3
LA  - en
ER  -
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