Abstract This chapter and https://cryptography.study/phys/modes introduce four encryption methods/modes and the one-time pad, all of which are based on the XOR operation. The new methods/modes limit the required key length and are therefore particularly interesting for QKD and RKD. Because hash functions are already used in QKD and RKD, no additional mathematical methods are required for data encryption. One of these four methods/modes also generates a MAC for the security objectives of integrity and authenticity. Because these methods/modes are very simple in structure—they contain only the XOR function for data encryption (like the 100% secure one-time pad) and a hash/MAC algorithm—cryptanalysis is also easily possible.
Abstract This chapter and https://cryptography.study/phys/modes introduce four encryption methods/modes and the one-time pad, all of which are based on the XOR operation. The new methods/modes limit the required key length and are therefore particularly interesting for QKD and RKD. Because hash functions are already used in QKD and RKD, no additional mathematical methods are required for data encryption. One of these four methods/modes also generates a MAC for the security objectives of integrity and authenticity. Because these methods/modes are very simple in structure—they contain only the XOR function for data encryption (like the 100% secure one-time pad) and a hash/MAC algorithm—cryptanalysis is also easily possible.
Abstract If the security assessments are not trusted, especially in cases of very high data security requirements, physical methods must be used for key generation and distribution, data encryption, and integrity and authenticity procedures. This ensures the confidentiality, integrity, and authenticity of the data against computationally powerful adversaries and mathematical attack methods that are still unknown (unpublished) today. This chapter provides an introduction to these topics, briefly compares mathematical methods, and discusses the generation and distribution of cryptographic keys, as well as QKD (Quantum Key Distribution), RKD (Radio signal Key Distribution), and MKD (Memeory Key Distribution).
Established symmetric encryption schemes rely on short key lengths, typically between 128 and 256 bits. However, well-known physical key exchange schemes such as QKD (Quantum Key Distribution) and RKD (Radio Signal Key Distribution) generate megabits of new key material on a daily, weekly, or other basis. This article presents a new encryption scheme, called OTPH, which was specifically designed for these megabits of regularly generated new key material. In this scheme, the key material is treated as an extremely long key, and the key’s enormous entropy is fully exploited. OTPH first uses a bit-selection procedure that randomly selects bits from the circularly arranged key, thereby extending the key many times over. From this, a HKDF (Hash Key Derivation Function) derives many new keys, and the result is a bit sequence that serves as the key for encryption using an XOR operation. OTPH uses only the XOR operation and hash function, which are also used in QKD and RKD during postprocessing (albeit a different hash function). An initial cryptanalysis has also been performed for OTPH. OTPH operates in a manner entirely contrary to established methods. It requires a completely new perspective. OTPH will not compete with AES, ChaCha20 etc., but will instead be used primarily in the context of QKD and RKD.
The article proposes a type of post–quantum cryptographic algorithm based on hash function and One–Time Pad cipher. Due to inheriting a property called “perfect secrecy” of the One-Time Pad cipher, the algorithms constructed according to the method proposed here can resist various types of attacks with the help of quantum computers. In addition to high security, algorithms of this type also have the ability to authenticate the origin and integrity of the encrypted messages. On the other hand, the one-time key for encryption/decryption is established for each individual message while the management and distribution of the shared secret key between the sender/encryptor and receiver/decryptor is performed similar to symmetric – key cryptosystems being applied in practice.
In this section, I wish to put quantum key distribution (QKD) in the wider context of a cryptosystem. I shall discuss informally some aspects that are considered important. The questions I wish to answer here are: “What are the ingredients needed to make a QKD-based cryptosystem work? What services does it bring? What are its limitations?” As I shall detail below, QKD may be used to provide the users with confidential communications. This can be achieved when we combine QKD and the one-time pad. For the quantum modulation, QKD needs a source of truly random numbers. Also, QKD requires a classical authenticated channel to work, so authentication plays an essential role. As a consequence, QKD must start with a secret key, making it a secret-key encryption scheme. I will also discuss what happens if classical cryptography is introduced in the system. Finally, I will describe the implementation of a simple cryptosystem on top of QKD. A key distribution scheme The first function of QKD is to distribute a secret key between two parties. The use of this key is outside the scope of this first section – the need for a secret key is omnipresent in cryptography. As depicted in Fig. 5.1, QKD relies on a classical authenticated channel for sifting and secret-key distillation and on random bits for the modulation of quantum states. The key produced by QKD can be intended for encryption purposes – this will be discussed in Section 5.2 – but is also required by authentication. A part of the distributed key is used for authentication. When QKD is run for the first time, however, an initial secret key must be used instead.
Quantum cryptography-the application of quantum information processing and quantum computing techniques to cryptography has been extensively investigated. Two major directions of quantum cryptography are quantum key distribution (QKD) and quantum encryption, with the former focusing on secure key distribution and the latter focusing on encryption using quantum algorithms. In contrast to the success of the QKD, the development of quantum encryption algorithms is limited to designs of mostly one-time pads (OTP) that are unsuitable for most communication needs. In this work we propose a non-OTP quantum encryption design utilizing a quantum state creation process to encrypt messages. As essentially a non-OTP quantum block cipher the method stands out against existing methods with the following features: 1. complex key-ciphertext relation (i.e. confusion) and complex plaintext-ciphertext relation (i.e. diffusion); 2. mode of operation design for practical encryption on multiple blocks. These features provide key reusability and protection against eavesdropping and standard cryptanalytic attacks.
Abstract MKD (Memory Key Distribution) takes a completely different approach to QKD and RKD. With MKD, non-deterministic random number generators generate the cryptographic keys, and the keys are transmitted using highly secure hardware tokens (usually smart cards) or special portable storage media (usually SSDs) with highly secure access protection for the data. Only highly secure storage media can be used for a one-time pad and thus for cryptography that is entirely free of mathematics (except for XOR).