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- 1a set of assumptions about how attackers might interact with a cipher and what they can and can’t do.Attack Models
- 2“All models are wrong; the practical question is how wrong do they have to be to not be useful.”George E.P Box
- 3is the operation that sends an input value to some function and gets the output in return, without exposing the details of that function.Query
- 4takes a plaintext and returns a corresponding ciphertext, without revealing the secret key.Encryption query
- 5attacker only sees what goes in and out of the cipher.Black-box models,
- 6observe ciphertexts but don’t know the associated plaintexts, and don’t know how the plaintexts were selected.Ciphertext-only attackers (COA)
- 7observe ciphertexts and do know the associated plaintexts.Known-plaintext attackers (KPA)
- 8can perform encryption queries for plaintexts of their choice and observe the resulting ciphertexts.Chosen-plaintext attackers (CPA)
- 9the attacker has access to a cipher’s implementation.Gray-Box Models
- 10depend on physical, analog properties rather than just on an algorithm’s input and outputs, and crypto theory will often fail to abstract the complexity of the real world.Gray-Box Models
- 11a family of attacks within gray-box models.Side-channel attacks
- 12a source of information that depends on the implementation of the cipher, be it in software or hardware.Side-channel attacks
- 13observe or measure analog characteristics of a cipher’s implementation but don’t alter its integrity; they are noninvasive.Side-channel attacks
- 14a family of attacks on cipher implementations that are more powerful than side-channel attacks, and more expensive because they require sophisticated equipmentInvasive attacks
- 15consist of a whole set of techniques and procedures, from using nitric acid to remove a chip’s packaging to microscopic imagery acquisition, partial reverse engineering, and possible modification of the chip’s behavior with something like laser fault injection.Invasive attacks
- 16This is usually illustrated with this hypothetical game: if an attacker picks two plaintexts and then receives a ciphertext of one of the two (chosen at random), they shouldn’t be able to tell which plaintext was encrypted, even by performing encryption queries with the two plaintexts rather than Chosen-plaintext attackers (CPA).Indistinguishability (IND).
- 17Security goals are only useful when combined with an attack model. The convention is to write a security notion as GOAL-MODEL.Non-malleability (NM)
- 18denotes indistinguishability against chosen- plaintext attackersIND-CPA
- 19denotes non-malleability against chosen-ciphertext attackersNM-CCA
- 20The most important security notion is IND-CPA, also called semantic security. It captures the intuition that ciphertexts shouldn’t leak any information about plaintexts as long as the key is secret.Semantic Security and Randomized Encryption
- 21an algorithm that returns random-looking bits given some secret value.deterministic random bit generator (DRBG)
- 22protects data sent from one machine to another: data is encrypted before being sent and decrypted after being received, as in encrypted connections to ecommerce websites.In-transit encryption
- 23protects data stored on an information system. Data is encrypted before being written to memory and decrypted before being read.At-rest encryption
- 24A cryptanalyst finds the key.Total Break
- 25A cryptanalyst finds an alternate algorithmGlobal deduction.
- 26A cryptanalyst finds the plaintext of an intercepted ciphertext.Instance (or local) deduction.
- 27A cryptanalyst gains some information about the key or plaintext.Information deduction.
- 28An algorithm is considered ___________________ if it cannot be broken with available resources, either current or future.Computationally secure
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- Karteikarten am Ohne Titel, erstellt von John Marion Alolino am 07/11/2022.
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