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What is an authenticator in the context of message transmission?
An authenticator is a value included in a transmitted message used to verify the authenticity and data integrity of the message. It includes a secret known only to the alleged sender, such as a key, and a proof, like a value encrypted using the key.
What is the purpose of a cryptographic hash function in authenticators?
A cryptographic hash function, also known as a cryptographic checksum, outputs redundant information about a message to expose any tampering. It is designed to expose deliberate corruption of messages by adversaries and outputs a message digest that is appended to the message.
What is the significance of collisions in hash functions?
Collisions in hash functions occur when different input messages produce the same message digest. This is similar to collisions in a hash table and poses a challenge for ensuring message integrity and authenticity.
What are Message Digest 5 (MD5) and Secure Hash Algorithm 1 (SHA1)?
MD5 and SHA1 are common cryptographic hash algorithms. MD5 outputs a 128-bit digest, while SHA1 outputs a 160-bit digest. Weaknesses in MD5 led to the recommendation to shift to SHA1 for improved security.
What is the purpose of a digital signature in message transmission?
A digest encrypted with a public key algorithm using the private key is called a digital signature. It provides non-repudiation, meaning the sender cannot successfully dispute the message's authorship. Receivers can verify the sender using the public key.
What is a Public Key Infrastructure (PKI) and how does it work?
A Public Key Infrastructure (PKI) certifies bindings between public keys and identities. It starts with verifying identities and binding them to keys out of band, outside the network. It involves the use of public key certificates to establish trust in key ownership.
What is a Certificate Authority (CA) in the context of PKI?
A Certificate Authority (CA) is a trusted entity for verifying identities and issuing public key certificates. CAs enable the building of chains of trust by certifying the authenticity of public keys.
What is a Certificate Revocation List (CRL) used for in PKI?
A Certificate Revocation List (CRL) is a digitally signed list of revoked certificates issued by a CA. It is periodically updated and made publicly available to prevent the use of compromised keys.
What is the purpose of predistribution of symmetric keys and how is it managed?
Predistribution of symmetric keys involves sharing a secret key with each entity to establish secure communication. This is typically managed through a Key Distribution Center (KDC) that shares a secret key with each entity, reducing the number of keys needed for communication.
What does the KDC participate in within the protocol?
The KDC participates in a protocol that authenticates Alice and Bob using the keys that the KDC already shares with each of them and generates a new session key for them to use.
How do Alice and Bob communicate after the KDC generates a new session key for them?
Alice and Bob communicate directly using their session key.
What is the number of the session key mentioned in the text?
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What is a Replay Attack?
A Replay Attack is when an adversary retransmits a copy of a message that was previously sent, making it appear as though the original message is being sent again.
What is a Suppress-replay Attack?
A Suppress-replay Attack is when an adversary delays a message by intercepting and later replaying it, causing the message to be received at a time when it is no longer appropriate.
What are the aspects of integrity related to Originality and Timeliness in authentication protocols?
Originality and timeliness may be considered aspects of integrity in authentication protocols.
What is one approach to ensure Originality and Timeliness in messages?
One approach is to include a timestamp in the message to ensure Originality and Timeliness.
What is a nonce in the context of authentication protocols?
A nonce is a random number used only once in a message to prevent replay attacks.
How can participants detect replay attacks when using nonces in authentication protocols?
Participants can detect replay attacks by checking whether a nonce has been used previously.
What is the drawback of using nonces in authentication protocols?
A drawback of using nonces is that it requires keeping track of past nonces, which can accumulate to a great number.
How can the shortcomings of timestamps and nonces be addressed in authentication protocols?
One solution is to combine the use of timestamps and nonces so that nonces are required to be unique only within a certain span of time.
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Flashcards summarizing network security concepts such as encryption, decryption, ciphers, symmetric-key ciphers, public-key ciphers, and authentication protocols.
Network Security
Encryption
Symmetric-key Cipher
Public-key Cryptography
Cryptographic Hash Functions
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