# Potentially Information-theoretic Secure Y00 Quantum Stream Cipher with Limited Key Lengths beyond One-Time Pad

## TL;DR

This paper demonstrates that the Y00 quantum stream cipher can achieve information-theoretic security with limited key lengths, surpassing traditional cryptographic limits, under well-designed system conditions.

## Contribution

It shows that the Y00 protocol can be secure against quantum computational attacks with proper design, extending its security beyond previous assumptions.

## Key findings

- Y00 can be information-theoretically secure with limited keys
- Security holds against quantum computational cryptanalysis
- Y00 surpasses Shannon limit in cryptography

## Abstract

The previous work showed that the Y00 protocol could stay secure with the eavesdropper's guessing probability on the secret keys being strictly less than one under an unlimitedly long known-plaintext attack with quantum memory. However, an assumption that at least a fast correlation attack is completely disabled by irregular mapping. The present study shows that the Y00 protocol can be information-theoretic secure under any quantum-computational crypto-analyses if the Y00 system is well designed. The Y00 protocol directly encrypts messages with short secret keys expanded into pseudo-random running keys unlike One-Time Pad. However, it may offer information-theoretic security beyond the Shannon limit of cryptography.

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Source: https://tomesphere.com/paper/1902.05192