In cryptography, a cryptosystem is called a threshold cryptosystem. If in order to decrypt an encrypted message or to sign a message several parties must cooperate in the decryption

1. Threshold
Cryptography
NAME : MOHIBULLAH SAIL
SECTION : A
SUBJECT : INFORMATION SECURITY
ROLL NO : SU-015-01-002-123

2. Agenda
 Introduction
 Applications
 Limitations
 Solutions
 References

3. Introduction[1]
 In cryptography, a cryptosystem is called a threshold cryptosystem.
 If in order to decrypt an encrypted message or to sign a message
 several parties must cooperate in the decryption
 The message is encrypted using a public key and the corresponding
 private key is shared among the participating parties
 Threshold versions of encryption can be built for many asymmetric
cryptographic schemes

4. Applications[2]
 Only organizations with very valuable secrets, such as certificate authorities militaries
 Governments would make use of the technology
 In October 2012 after a number of large public website password cipher text
 cooperation RSA Security announced that it would be releasing software that makes
 the technology available to the general public.
 Threshold cryptography is a secret sharing technique that finds applications in many fields
including cloud computing (remote servers on internet to store ,manage and process data)
 Authentication and sensor networks, digital
 signatures, and electronic voting

5. Limitations[3]
 The dark side of threshold cryptography has never been addressed seriously
 We investigate some possible abuses of threshold cryptography
 which result from users not possessing the entire private key due to threshold splitting
 Examples:
 1: subliminal channels in strong (randomized) signature schemes.
 2: Employing authentication for encryption.
 3:kleptography exploiting etc.

6. Challenges[4]
 Challenge–response authentication
 One party generate a question and another party is responsible to give valid answer to be
authenticated.
 The simplest example of a challenge–response protocol is password authentication
 Challenge is asking for the password and the valid response is the correct password
 For communications security methods are unavailable, the U.S military uses the AKAC1553
 TRIAD numeral cipher to authenticate and encrypt some communications
 TRIAD includes a list of three-letter challenge codes, which the verifier is supposed to choose
randomly from, and random three-letter responses to them. For added security
 Codes is only valid for a particular time period which is ordinarily 24 hours

7. Solutions[5]
 In the threshold setting, we would like to implement, via efficient protocols, the most secure
cryptosystems and signature schemes.
 We would also like to make our protocols secure in the strongest possible model of faults.
 The size of the threshold: The servers can be corrupted by the adversary without any harm to the
service (e.g. signature or decryption) that these servers implement
 Model of communication : How realistic are the requirements we place on it? Do we require
synchronous or partially synchronous communication, authenticated broadcast and secure links
between servers?

8. References
1 :https://en.wikipedia.org/wiki/Threshold_cryptosystem
2 :https://en.wikipedia.org/wiki/Threshold_cryptosystem
:https://www.tandfonline.com/doi/abs/10.1080/19393555.2016.1251996
3 : https://link.springer.com/chapter/10.1007/3-540-36504-4_15
4 : https://en.wikipedia.org/wiki/Challenge%E2%80%93response_authentication
5 : http://groups.csail.mit.edu/cis/cis-threshold.html

9. THANK YOU
Mohibullah.sail@gmail.com