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Adamson U
Cryptography
Practice Quiz

Questions:

1
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What is the purpose of a hash function in cryptography?
3
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What is the difference between a cipher and a code?
5
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What is a digital signature, and how is it used in secure communication?
7
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What is a man-in-the-middle attack, and how can it be prevented?
9
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What is the difference between a stream cipher and a block cipher?
11
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How does the Diffie-Hellman key exchange algorithm work?
13
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What is a Public Key Infrastructure (PKI), and why is it critical?
15
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What is the purpose of a digital envelope in cryptography?
17
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What is the difference between a digital signature and a message authentication code
(MAC)?
19
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What is the difference between a one-time pad and a stream cipher?

Answer:

1
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In symmetric encryption,
the same key is used for encryption and decryption
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Symmetric encryption and asymmetric encryption are two different methods of encrypting
data
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In symmetric encryption, the same key is used for encryption and decryption
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This can be a problem if the key is intercepted or lost, as anyone who has the key will
be able to read the news
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On the other hand, asymmetric encryption uses a pair of keys, a public key, and a private key
...
The public key can be
freely distributed to anyone, while the private key is kept secret
...
This makes it much more secure than symmetric encryption, as the
private key does not need to be shared and can be kept safe
...
In contrast,
asymmetric encryption uses a pair of keys, a public key for encryption, and a private key for

decryption
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2
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’ The
purpose of a hash function is to ensure the integrity of data by providing a unique value for any
given input
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A hash function is a mathematical function commonly used in cryptography to ensure data
integrity
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” The primary purpose of a
hash function is to provide a unique value for any given input so that any changes to the
original information will result in a different hash value
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This allows for easy detection of any
changes to the input data
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A hash function is considered a “strong” function if it is deterministic and crash resistant
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This is known as
the "collision resistance" property
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For example,
when a file is downloaded, the recipient can use the hash value provided by the sender to verify
that the file has not been tampered with during transmission
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In summary, a hash function is a one-way mathematical function that takes an input or message
and returns a fixed-size string of characters, referred to as the hash value
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A good hash function
should be deterministic and collision resistant
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The RSA algorithm is a widely used asymmetric encryption algorithm based on the
mathematical properties of large prime numbers
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To encrypt a
statement, the sender uses the recipient's public key
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The security of the RSA algorithm is based on the fact that
factoring large composite numbers is computationally infeasible
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It is based on the mathematical properties of large prime numbers and is
considered one of the safest encryption methods
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The public key
encrypts the message, while the private key decrypts it
...


The security of the RSA algorithm is based on the fact that factoring large composite numbers is
computationally infeasible
...
If someone were to factor in the composite number,
they would be able to determine the private key, thus compromising the system’s security
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In summary, The RSA algorithm is an asymmetric encryption algorithm widely used for secure
data transmission
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The security of the RSA algorithm is
based on the fact that factoring large composite numbers is computationally infeasible, making
it difficult for an attacker to determine the private key and compromise the security of the
system
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A cipher is a method of encrypting data, while a code hides the meaning of a message
...

A cipher and a code are both methods of encrypting data, but they are used for different
purposes and have other characteristics
...

It is a method of converting plaintext (the original message) into ciphertext (the encrypted
message) using a mathematical algorithm
...
Common examples
of ciphers include AES, DES, and RSA
...
Regulations
typically conceal a message’s meaning rather than protect it
...
On the other hand, a code hides the meaning of a message rather than the message
itself
...
Ciphers are typically used to ensure
that the message cannot be read by anyone who does not have the key to decrypt it, while
codes are often used to conceal the meaning of a message
...
Confidentiality in cryptography refers to data protection from unauthorized access or
disclosure
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Confidentiality and integrity are two essential concepts in cryptography that are used to ensure
data security
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It ensures that sensitive information is only accessible to authorized individuals or
systems
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This prevents unauthorized individuals or systems from viewing
the information
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It ensures that an unauthorized individual or system has not altered the data
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These techniques can detect any changes made to the data and ensure that the data is
authentic and has not been tampered with
...
Integrity in cryptography refers to the protection of data from
unauthorized modification or tampering, which provides that the data has not been altered in
any way by an unauthorized individual or system
...


6
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It is created by applying a mathematical algorithm to the data to be
signed, along with a private key
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Digital signatures are used in secure communication to ensure that
the information received has not been tampered with and is from the claimed sender
...
It is created by applying a mathematical algorithm
to the data that is being signed, along with a private key
...
The resulting digital signature can be verified using the
corresponding public key, typically shared with the intended recipient
...
Creating a digital signature involves taking a hash of the original data and

encrypting it with the sender's private key
...
If the
two hashes match, the signature is valid, meaning that the data has not been modified and is
from the claimed sender
...
It provides a way to authenticate the sender’s identity and ensure
that the information received has not been tampered with
...


In summary, A digital signature verifies the authenticity and integrity of digital information,
such as electronic documents
...
The resulting digital signature can then be verified using the
corresponding public key
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7
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A trusted third party issues it a certificate authority (CA) to
verify the entity’s identity
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It is created by applying a
mathematical algorithm to the data to be signed, along with a private key
...
A trusted
third party issues it, called a certificate authority (CA), and is used to verify the entity’s identity
...


A digital certificate is an electronic form of identification, similar to a passport or driver's
license
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When a user connects to a website, for example, their browser will check
the website's digital certificate to ensure that it is valid and issued by a trusted CA
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It is created by applying a mathematical algorithm
to the data to be signed, along with a private key
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In summary, A digital certificate contains information about an entity, such as an individual or
organization, and its public key
...
On the other hand, a
digital signature verifies the authenticity and integrity of digital information, such as an
electronic document; it is created by applying a mathematical algorithm to the data to be
signed, along with a private key
...
A man-in-the-middle (MITM) attack is a type of cyber attack in which an attacker intercepts
and alters the communication between two parties
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MITM attacks can be
prevented by using secure communication protocols, such as HTTPS, and by verifying the
identity of the parties using digital certificates or other authentication methods
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The attacker can read, modify, or inject new
data into the contract without the knowledge of either party
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There are several wa
be done in real-time
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On the other hand, a block cipher encrypts data in fixed-size blocks, typically 128 or 256 bits
...
Block ciphers are commonly used in protocols that require a high level of security,
such as in financial transactions and secure communications
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Still, they also have a higher risk of repeating patterns in the keystream, which
can lead to security vulnerabilities
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The key must be changed after
a certain number of encrypted bits to prevent this
...
A key exchange algorithm is used v
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A key exchange algorithm is a cryptographic technique used to exchange keys between two
parties securely
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This
shared private key can then encrypt and decrypt messages between the parties
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The Diffie-Hellman algorithm allows two parties to establish a shared secret key over an
insecure communication channel without any prior secrets
...


On the other hand, the RSA algorithm is an asymmetric encryption algorithm based on the
mathematical properties of large prime numbers
...
It is a widely used algorithm in
secure communication protocols
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However, in recent years, new key exchange algorithms have been proposed, and
some of them are considered more secure than the traditional ones, such as the Elliptic-Curve
Diffie-Hellman (ECDH) and the New Hope algorithm
...
The Diffie-Hellman key exchange algorithm is a widely used critical exchange method based
on large prime numbers' mathematical properties
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Each party then
uses the other party's public and private keys to generate a shared secret key, which can be
used for encryption and decryption
...

The Diffie-Hellman (DH) key exchange algorithm is widely used for securely exchanging keys
between two parties
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The Diffie-Hellman algorithm generates a pair of public and private keys for each party
...
Each party uses
the other party's public and private keys to generate a shared secret key
...


The security of the Diffie-Hellman algorithm is based on the fact that it is computationally
infeasible to determine the private key from the public key
...


The DH key ex

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