Schemes for Digital Signatures

Integrity is the property of information concerning protection against its unauthorized modifications and forgeries. This chapter discusses bulletin board (BB), hash functions, MACs (Message Authentication Codes) and digital signatures, as schemes for maintaining integrity of data. BBs protect data by simply disclosing them to the public, i.e. an entity cannot modify them without being watched by others. Hash functions, Macs, and digital signatures protect data by detecting illegitimate modifications while attaching values to the data. Namely, when an entity illegitimately modifies the data, the modified results become inconsistent with the attached values. When hash functions, MACs and digital signatures are compared regarding the ability to convince entities that the data are authorized ones, hash functions cannot enable entities to convince others, and by MACs, entities can convince others only when relevant secrets are properly protected. On the other hand, digital signatures enable anyone to convince others without constraints.

Author(s):  
Kannan Balasubramanian

Cryptographic Hash Functions are used to achieve a number of Security goals like Message Authentication, Message Integrity, and are also used to implement Digital Signatures (Non-repudiation), and Entity Authentication. This chapter discusses the construction of hash functions and the various attacks on the Hash functions. The Message Authentication Codes are similar to the Hash functions except that they require a key for producing the message digest or hash. Authenticated Encryption is a scheme that combines hashing and Encryption. The Various types of hash functions like one-way hash function, Collision Resistant hash function and Universal hash functions are also discussed in this chapter.


Cryptography ◽  
2020 ◽  
Vol 4 (4) ◽  
pp. 31
Author(s):  
Georgios M. Nikolopoulos ◽  
Marc Fischlin

In conventional cryptography, information-theoretically secure message authentication can be achieved by means of universal hash functions, and requires that the two legitimate users share a random secret key, which is at least twice as long as the tag. We address the question of whether quantum resources can offer any advantage over classical unconditionally secure message authentication codes. It is shown that a broad class of symmetric prepare-and-measure quantum message-authentication schemes cannot do better than their classical counterparts.


APRIA Journal ◽  
2020 ◽  
Vol 1 (1) ◽  
pp. 11-16
Author(s):  
José Teunissen

In the last few years, it has often been said that the current fashion system is outdated, still operating by a twentieth-century model that celebrates the individualism of the 'star designer'. In I- D, Sarah Mower recently stated that for the last twenty years, fashion has been at a cocktail party and has completely lost any connection with the public and daily life. On the one hand, designers and big brands experience the enormous pressure to produce new collections at an ever higher pace, leaving less room for reflection, contemplation, and innovation. On the other hand, there is the continuous race to produce at even lower costs and implement more rapid life cycles, resulting in disastrous consequences for society and the environment.


Author(s):  
Keith M. Martin

This chapter discusses cryptographic mechanisms for providing data integrity. We begin by identifying different levels of data integrity that can be provided. We then look in detail at hash functions, explaining the different security properties that they have, as well as presenting several different applications of a hash function. We then look at hash function design and illustrate this by discussing the hash function SHA-3. Next, we discuss message authentication codes (MACs), presenting a basic model and discussing basic properties. We compare two different MAC constructions, CBC-MAC and HMAC. Finally, we consider different ways of using MACs together with encryption. We focus on authenticated encryption modes, and illustrate these by describing Galois Counter mode.


2021 ◽  
Vol 29 (1) ◽  
pp. 36-61
Author(s):  
Michael Poznic ◽  
Rafaela Hillerbrand

Climatologists have recently introduced a distinction between projections as scenario-based model results on the one hand and predictions on the other hand. The interpretation and usage of both terms is, however, not univocal. It is stated that the ambiguities of the interpretations may cause problems in the communication of climate science within the scientific community and to the public realm. This paper suggests an account of scenarios as props in games of make-belive. With this account, we explain the difference between projections that should be make-believed and other model results that should be believed.


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