Itsec an der Universität Mannheim | Karteikarten & Zusammenfassungen

Lernmaterialien für Itsec an der Universität Mannheim

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Unconditional Security

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No matter how much computer power is available, the cipher cannot be broken since the ciphertext provides insufficient information to uniquely determine the corresponding plaintext

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Computational security

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Given limited computing resources, the cipher cannot be broken

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Stream Cipher

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key from OTP replaced with pseudo-random sequence that is ‘seeded’ with the key


instead of using a Pseudo-random generator (PRG) on the key, it is used on an Initialization vector and a key. Make sure IV is never used twice!

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Block Cipher

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To encrypt a plaintext consisting of n-bits, a key is used the size of k-bits, to result in a ciphertext the same size as the plaintext. This n-bit sized vector is called a block

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Modes of Block Ciphers

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Electronic Code-Book (ECB)

Cipher Block Chaining (CBC)

Counter (CTR)

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ECB

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Electronic Code-Book

= Message is broken into blocks, which are encoded independently of other blocks

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CBC

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Cipher Block Chaining

= 1. Message is broken into blocks

2. each previous cipher block is chained with current plaintext

3. To make ciphertext depends on all blocks before it

4. Start process with IV


Does not provide protection against data modification such as deletion and insertion

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CTR

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Counter

= Each block is encrypted with a new IV consisting of a random number (nonce) and a counter. Then the IV is combined with the key to create each individual ciphertext. 

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Ciphertext-only attack

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Attacker tries to deduce the decryption key or plaintext by only observing ciphertext


Encryption schemes vulnerable to this attack are completely insecure

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Known-plaintext

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Attacker has a quantity of plaintext and corresponding ciphertext

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chosen plaintext attack

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Attacker chooses plaintext and is then given corresponding ciphertext

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Security Goals

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Confidentiality

Integrity

Authenticity

Availability

Access Control

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  • 55505 Karteikarten
  • 1092 Studierende
  • 31 Lernmaterialien

Beispielhafte Karteikarten für deinen Itsec Kurs an der Universität Mannheim - von Kommilitonen auf StudySmarter erstellt!

Q:

Unconditional Security

A:

No matter how much computer power is available, the cipher cannot be broken since the ciphertext provides insufficient information to uniquely determine the corresponding plaintext

Q:

Computational security

A:

Given limited computing resources, the cipher cannot be broken

Q:

Stream Cipher

A:

key from OTP replaced with pseudo-random sequence that is ‘seeded’ with the key


instead of using a Pseudo-random generator (PRG) on the key, it is used on an Initialization vector and a key. Make sure IV is never used twice!

Q:

Block Cipher

A:

To encrypt a plaintext consisting of n-bits, a key is used the size of k-bits, to result in a ciphertext the same size as the plaintext. This n-bit sized vector is called a block

Q:

Modes of Block Ciphers

A:

Electronic Code-Book (ECB)

Cipher Block Chaining (CBC)

Counter (CTR)

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Q:

ECB

A:

Electronic Code-Book

= Message is broken into blocks, which are encoded independently of other blocks

Q:

CBC

A:

Cipher Block Chaining

= 1. Message is broken into blocks

2. each previous cipher block is chained with current plaintext

3. To make ciphertext depends on all blocks before it

4. Start process with IV


Does not provide protection against data modification such as deletion and insertion

Q:

CTR

A:

Counter

= Each block is encrypted with a new IV consisting of a random number (nonce) and a counter. Then the IV is combined with the key to create each individual ciphertext. 

Q:

Ciphertext-only attack

A:

Attacker tries to deduce the decryption key or plaintext by only observing ciphertext


Encryption schemes vulnerable to this attack are completely insecure

Q:

Known-plaintext

A:

Attacker has a quantity of plaintext and corresponding ciphertext

Q:

chosen plaintext attack

A:

Attacker chooses plaintext and is then given corresponding ciphertext

Q:

Security Goals

A:

Confidentiality

Integrity

Authenticity

Availability

Access Control

Itsec

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