Threshold cryptosystem

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A threshold cryptosystem, the basis for the field of threshold cryptography, is a cryptosystem that protects information by encrypting it and distributing it among a cluster of fault-tolerant computers. The message is encrypted using a public key, and the corresponding private key is shared among the participating parties. With a threshold cryptosystem, in order to decrypt an encrypted message or to sign a message, several parties (more than some threshold number) must cooperate in the decryption or signature protocol.

Contents

History

Perhaps the first system with complete threshold properties for a trapdoor function (such as RSA) and a proof of security was published in 1994 by Alfredo De Santis, Yvo Desmedt, Yair Frankel, and Moti Yung. [1]

Historically, only organizations with very valuable secrets, such as certificate authorities, the military, and governments made use of this technology. One of the earliest implementations was done in the 1990s by Certco for the planned deployment of the original Secure electronic transaction. [2] However, in October 2012, after a number of large public website password ciphertext compromises, RSA Security announced that it would release software to make the technology available to the general public. [3]

In March 2019, the National Institute of Standards and Technology (NIST) conducted a workshop on threshold cryptography to establish consensus on applications, and define specifications. [4] In November, NIST published a draft roadmap "towards the standardization of threshold schemes for cryptographic primitives" as NISTIR 8214A. [5] [6]

Methodology

Let be the number of parties. Such a system is called (t,n)-threshold, if at least t of these parties can efficiently decrypt the ciphertext, while fewer than t have no useful information. Similarly it is possible to define a (t,n)-threshold signature scheme, where at least t parties are required for creating a signature.[ citation needed ]

Versions

Threshold versions of encryption or signature schemes can be built for many asymmetric cryptographic schemes. The natural goal of such schemes is to be as secure as the original scheme. Such threshold versions have been defined by the above and by the following: [7]

Application

The most common application is in the storage of secrets in multiple locations to prevent the capture of the secret and the subsequent cryptanalysis of that system. Most often the secrets that are "split" are the secret key material of a public key cryptography or of a Digital signature scheme. The method primarily enforces the decryption or the signing operation to take place only if a threshold of the secret sharer operates (otherwise the operation is not made). This makes the method a primary trust sharing mechanism, besides its safety of storage aspects.

See also

Related Research Articles

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Digital signature

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A chosen-ciphertext attack (CCA) is an attack model for cryptanalysis where the cryptanalyst can gather information by obtaining the decryptions of chosen ciphertexts. From these pieces of information the adversary can attempt to recover the hidden secret key used for decryption.

Articles related to cryptography include:

An adaptive chosen-ciphertext attack is an interactive form of chosen-ciphertext attack in which an attacker first sends a number of ciphertexts to be decrypted chosen adaptively, then uses the results to distinguish a target ciphertext without consulting the oracle on the challenge ciphertext, in an adaptive attack the attacker is further allowed adaptive queries to be asked after the target is revealed. It is extensing the indifferent (non-adaptive) chosen-ciphertext attack (CCA1) where the second stage of adaptive queries is not allowed. Charles Rackoff and Dan Simon defined CCA2 and suggested a system building on the non-adaptive CCA1 definition and system of Moni Naor and Moti Yung.

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Cryptography Practice and study of secure communication techniques

Cryptography, or cryptology, is the practice and study of techniques for secure communication in the presence of third parties called adversaries. More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages; various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation are central to modern cryptography. Modern cryptography exists at the intersection of the disciplines of mathematics, computer science, electrical engineering, communication science, and physics. Applications of cryptography include electronic commerce, chip-based payment cards, digital currencies, computer passwords, and military communications.

Mordechai M. "Moti" Yung is a cryptographer and computer scientist known for his work on cryptovirology and kleptography.

Post-Quantum Cryptography Standardization is a program and competition by NIST to update their standards to include post-quantum cryptography. It was announced at PQCrypto 2016. 23 signature schemes and 59 encryption/KEM schemes were submitted by the initial submission deadline at the end of 2017 of which 69 total were deemed complete and proper and participated in the first round. Seven of these, of which 3 are signature schemes, have advanced to the third round, which was announced on July 22, 2020.

References

  1. Alfredo De Santis, Yvo Desmedt, Yair Frankel, Moti Yung: How to share a function securely. STOC 1994: 522-533
  2. Visa and Mastercard have just announced the selection of two companies -- CertCo and Spyrus, 1997-05-20, retrieved 2019-05-02.
  3. Tom Simonite (2012-10-09). "To Keep Passwords Safe from Hackers, Just Break Them into Bits". Technology Review. Retrieved 2020-10-13.
  4. "Threshold Cryptography". csrc.nist.gov. 2019-03-20. Retrieved 2019-05-02.
  5. Computer Security Division, Information Technology Laboratory (2018-07-25). "NIST Releases Draft NISTIR 8214 for Comment | CSRC". CSRC | NIST. Retrieved 2020-03-24.
  6. Brandão, Luís T. A. N.; Davidson, Michael; Vassilev, Apostol (2019-11-08). "Towards NIST Standards for Threshold Schemes for Cryptographic Primitives: A Preliminary Roadmap".Cite journal requires |journal= (help)
  7. Jonathan Katz, Moti Yung:Threshold Cryptosystems Based on Factoring. ASIACRYPT 2002: 192-205
  8. Ivan Damgård, Mads Jurik: A Length-Flexible Threshold Cryptosystem with Applications. ACISP 2003: 350-364
  9. Ivan Damgård, Mads Jurik: A Generalisation, a Simplification and Some Applications of Paillier's Probabilistic Public-Key System. Public Key Cryptography 2001: 119-136
  10. Rosario Gennaro, Stanislaw Jarecki, Hugo Krawczyk, Tal Rabin: Robust Threshold DSS Signatures. EUROCRYPT 1996: 354-371
  11. "Distributed Privacy Guard (DKGPG)". 2017.
  12. Green, Marc; Eisenbarth, Thomas (2015). "Strength in Numbers: Threshold ECDSA to Protect Keys in the Cloud" (PDF).Cite journal requires |journal= (help)
  13. Gennaro, Rosario; Goldfeder, Steven; Narayanan, Arvind (2016). "Threshold-optimal DSA/ECDSA signatures and an application to Bitcoin wallet security" (PDF).Cite journal requires |journal= (help)
  14. Gągol, Adam; Straszak, Damian; Świętek, Michał; Kula, Jędrzej (2019). "Threshold ECDSA for Decentralized Asset Custody" (PDF).Cite journal requires |journal= (help)CS1 maint: date and year (link)