Definitions of Security

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Which of the following is a precise definition of computational security?

The attacker has unlimited computational power.

Guessing the plaintext has the same chances of success after having seen the ciphertext as it had before seeing it.

The ciphertext leaks no information about the plaintext except the length.

There is no efficient algorithm that can be used by the attacker to succeed with reasonably high probability. (correct)

What is the difference between computational security and unconditional security?

Computational security requires an efficient algorithm to break the cipher, while unconditional security allows for partial information about the plaintext.

Computational security requires the attacker to have limited computational power, while unconditional security allows for unlimited computational power.

Computational security is based on the length of the key, while unconditional security is based on the length of the plaintext.

Computational security depends on the currently available algorithms and computing power, while unconditional security is impossible to break even with unlimited time and resources. (correct)

What is perfect secrecy in cryptography?

Guessing the plaintext has the same chances of success after having seen the ciphertext as it had before seeing it. (correct)

The attacker has unlimited computational power.

Ciphertext leaks no information about the plaintext except the length.

It is unfeasible to break the cipher.

What is the main difference between computational security and perfect secrecy?

Computational security allows for some information leakage, while perfect secrecy leaks no information about the plaintext. Signup and view all the answers

What is the definition of unconditional security?

It is impossible (even with unlimited time/resources) to break the cipher. Signup and view all the answers

Which type of attack assumes that the attacker has unlimited computational power?

Ciphertext-only attack Signup and view all the answers

What is the difference between provable security and computational security?

Provable security has a mathematical proof that there is no efficient algorithm to break the cipher, while computational security has no such proof. Signup and view all the answers

Which type of cryptography has provable security?

Public key cryptography Signup and view all the answers

What is the definition of computational security in terms of the probability of success for the attacker?

Reasonably high probability usually means 1/(polynomial in n) Signup and view all the answers

What is the one-time pad?

A cipher with perfect secrecy Signup and view all the answers

What is the difference between computational security and provable security?

Computational security has a mathematical proof that there is no efficient algorithm to break the cipher, while provable security has no such proof. Signup and view all the answers

Which type of cryptography has no provable security?

Symmetric cryptography Signup and view all the answers

Which of the following is a precise definition of computational security?

There is no efficient algorithm that can be used by the attacker to succeed with reasonably high probability. Signup and view all the answers

What is the difference between computational security and unconditional security?

Computational security depends on the currently available algorithms and computing power, while unconditional security is impossible to break even with unlimited time and resources. Signup and view all the answers

What is perfect secrecy in cryptography?

Guessing the plaintext has the same chances of success after having seen the ciphertext as it had before seeing it. Signup and view all the answers

What is the main difference between computational security and perfect secrecy?

Computational security allows for some information leakage, while perfect secrecy leaks no information about the plaintext. Signup and view all the answers

What is the definition of unconditional security?

It is impossible (even with unlimited time/resources) to break the cipher. Signup and view all the answers

Which type of attack assumes that the attacker has unlimited computational power?

Ciphertext-only attack Signup and view all the answers

What is the difference between provable security and computational security?

Provable security has a mathematical proof that there is no efficient algorithm to break the cipher, while computational security has no such proof. Signup and view all the answers

Which type of cryptography has provable security?

Public key cryptography Signup and view all the answers

What is the definition of computational security in terms of the probability of success for the attacker?

Reasonably high probability usually means 1/(polynomial in n) Signup and view all the answers

What is the one-time pad?

A cipher with perfect secrecy Signup and view all the answers

What is the difference between computational security and provable security?

Computational security has a mathematical proof that there is no efficient algorithm to break the cipher, while provable security has no such proof. Signup and view all the answers

Which type of cryptography has no provable security?

Symmetric cryptography Signup and view all the answers

Which type of attack does a ciphertext-only attack refer to?

An attack where the attacker has access to the ciphertext only Signup and view all the answers

What does it mean for a cipher to have perfect secrecy?

The ciphertext leaks no information about the plaintext except the length Signup and view all the answers

What type of security is dependent on the currently available algorithms and computing power?

Computational security Signup and view all the answers

What is the difference between computational security and unconditional security?

Computational security is dependent on the currently available algorithms and computing power, while unconditional security is not Signup and view all the answers

What is the main difference between provable security and computational security?

Provable security means that it is unfeasible to break the cipher, while computational security means that no attack has succeeded in a reasonable amount of time Signup and view all the answers

What does it mean for a cipher to have unconditional security?

The cipher is impossible to break even with unlimited time/resources Signup and view all the answers

What is the difference between computational security and provable security?

Computational security means that no attack has succeeded in a reasonable amount of time, while provable security means that it is unfeasible to break the cipher Signup and view all the answers

What is one possible precise mathematical definition of computational security?

There is no efficient algorithm that can be used by the attacker to succeed with reasonably high probability Signup and view all the answers

What is one example of a cipher that has perfect secrecy?

One-time pad Signup and view all the answers

For which type of cryptography does provable security exist?

Public key cryptography Signup and view all the answers

What is the difference between computational security and perfect secrecy?

Computational security is impossible to break even with unlimited time/resources, while perfect secrecy is unfeasible to break Signup and view all the answers

What is the difference between provable security and unconditional security?

Provable security means that it is unfeasible to break the cipher, while unconditional security means that no attack has succeeded in a reasonable amount of time Signup and view all the answers

What are the different levels of knowledge the attacker can have in terms of breaking a cipher?

Ciphertext only, known plaintext, chosen plaintext, chosen ciphertext, samples of previous signatures or message authentication codes. Signup and view all the answers

What does it mean to 'break' a cryptosystem?

Finding the plaintext, key, creating a digital signature, creating a message authentication code. Signup and view all the answers

Does obtaining partial information about the plaintext/key count as 'breaking' a cryptosystem?

It depends on the specific definition of 'breaking' used. Signup and view all the answers

What is computational security?

It is unfeasible (too time/resource consuming) to break the cipher; this depends on the currently available algorithms and computing power. Signup and view all the answers

What is unconditional security?

It is impossible (even with unlimited time/resources) to break the cipher. Signup and view all the answers

What is the difference between computational security and unconditional security?

Computational security is unfeasible to break, while unconditional security is impossible to break. Signup and view all the answers

What is provable security?

There is no efficient algorithm that can be used by the attacker to succeed with reasonably high probability. Signup and view all the answers

What is the definition of perfect secrecy/information-theoretic security?

The ciphertext leaks no information about the plaintext (except the length). Signup and view all the answers

What is the one-time pad?

A cipher that has perfect secrecy, but is expensive and not used in practice. Signup and view all the answers

Which type of cryptography has provable security?

Public key cryptography. Signup and view all the answers

Which type of cryptography has no provable security?

Symmetric cryptography. Signup and view all the answers

What is the status of computational security for most ciphers in use today?

They only have computational security in the sense that no attack has succeeded in a reasonable amount of time, but there is no proof that no efficient attack will be found. Signup and view all the answers

Definitions of Security

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Questions and Answers

Which of the following is a precise definition of computational security?

What is the difference between computational security and unconditional security?

What is perfect secrecy in cryptography?

What is the main difference between computational security and perfect secrecy?

What is the definition of unconditional security?

Which type of attack assumes that the attacker has unlimited computational power?

What is the difference between provable security and computational security?

Which type of cryptography has provable security?

What is the definition of computational security in terms of the probability of success for the attacker?

What is the one-time pad?

What is the difference between computational security and provable security?

Which type of cryptography has no provable security?

Which of the following is a precise definition of computational security?

What is the difference between computational security and unconditional security?

What is perfect secrecy in cryptography?

What is the main difference between computational security and perfect secrecy?

What is the definition of unconditional security?

Which type of attack assumes that the attacker has unlimited computational power?

What is the difference between provable security and computational security?

Which type of cryptography has provable security?

What is the definition of computational security in terms of the probability of success for the attacker?

What is the one-time pad?

What is the difference between computational security and provable security?

Which type of cryptography has no provable security?

Which type of attack does a ciphertext-only attack refer to?

What does it mean for a cipher to have perfect secrecy?

What type of security is dependent on the currently available algorithms and computing power?

What is the difference between computational security and unconditional security?

What is the main difference between provable security and computational security?

What does it mean for a cipher to have unconditional security?

What is the difference between computational security and provable security?

What is one possible precise mathematical definition of computational security?

What is one example of a cipher that has perfect secrecy?

For which type of cryptography does provable security exist?

What is the difference between computational security and perfect secrecy?

What is the difference between provable security and unconditional security?

What are the different levels of knowledge the attacker can have in terms of breaking a cipher?

What does it mean to 'break' a cryptosystem?

Does obtaining partial information about the plaintext/key count as 'breaking' a cryptosystem?

What is computational security?

What is unconditional security?

What is the difference between computational security and unconditional security?

What is provable security?

What is the definition of perfect secrecy/information-theoretic security?

What is the one-time pad?

Which type of cryptography has provable security?

Which type of cryptography has no provable security?

What is the status of computational security for most ciphers in use today?

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