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Adamson U
Cryptography
Practice Quiz

Questions:

1
...
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
...
What is a digital signature, and how is it used in secure communication?
7
...
What is a man-in-the-middle attack, and how can it be prevented?
9
...
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
...
What is a Public Key Infrastructure (PKI), and why is it critical?
15
...
What is the purpose of a digital envelope in cryptography?
17
...
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
...
In symmetric encryption,
the same key is used for encryption and decryption
...

Symmetric encryption and asymmetric encryption are two different methods of encrypting
data
...


In symmetric encryption, the same key is used for encryption and decryption
...
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
...


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
...


2
...
’ The
purpose of a hash function is to ensure the integrity of data by providing a unique value for any
given input
...

A hash function is a mathematical function commonly used in cryptography to ensure data
integrity
...
” 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
...
This allows for easy detection of any
changes to the input data
...


A hash function is considered a “strong” function if it is deterministic and crash resistant
...
This is known as
the "collision resistance" property
...
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
...


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
...
A good hash function
should be deterministic and collision resistant
...
The RSA algorithm is a widely used asymmetric encryption algorithm based on the
mathematical properties of large prime numbers
...
To encrypt a
statement, the sender uses the recipient's public key
...
The security of the RSA algorithm is based on the fact that
factoring large composite numbers is computationally infeasible
...
It is based on the mathematical properties of large prime numbers and is
considered one of the safest encryption methods
...
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
...


In summary, The RSA algorithm is an asymmetric encryption algorithm widely used for secure
data transmission
...
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
...
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
...

Confidentiality and integrity are two essential concepts in cryptography that are used to ensure
data security
...
It ensures that sensitive information is only accessible to authorized individuals or
systems
...
This prevents unauthorized individuals or systems from viewing
the information
...
It ensures that an unauthorized individual or system has not altered the data
...

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
...
It is created by applying a mathematical algorithm to the data to be
signed, along with a private key
...
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
...


7
...
A trusted third party issues it a certificate authority (CA) to
verify the entity’s identity
...
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
...
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
...
It is created by applying a mathematical algorithm
to the data to be signed, along with a private key
...


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
...
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
...
The attacker can read, modify, or inject new
data into the contract without the knowledge of either party
...


There are several ways in which a MITM attack can be executed
...
Other methods include WiFi eavesdropping, DNS spoofing, and SSL hijacking
...
Additionally, the
identity of the parties can be verified using digital certificates or other methods of

authentication, such as two-factor authentication, which makes it more difficult for the attacker
to impersonate one of the parties
...
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,
such as two-factor authentication, which makes it more difficult for the attacker to impersonate
one of the parties
...
A zero-knowledge proof is a method of proving the possession of certain information without
revealing the data itself
...

A zero-knowledge proof is a method of proving the possession of certain information without
revealing it
...
The concept of
zero-knowledge proof is based on the idea of interactive proof systems, where a prover (the
person who wants to prove that they possess certain information) and a verifier (the person
who wants to be convinced that the prover has the info) engage in a series of interactions to
establish the proof
...
For example, a person may wish to verify their age on a website
or service, but they want to keep their date of birth or other personal information private
...


Another use case of zero-knowledge proof is in the field of cryptocurrency; for example, in
privacy-oriented cryptocurrencies, a zero-knowledge warranty is used to prove the ownership
of certain assets without revealing the owner’s identity
...
It is used in cryptographic schemes, such as zeroknowledge proof of identity, to ensure privacy while still providing proof of identity; it is a
powerful tool that allows a person to prove that they possess specific knowledge or information
without revealing the data itself
...


10
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Stream ciphers are generally faster and more
efficient than block ciphers when encrypting large amounts of data
...

A stream cipher and a block cipher are symmetric encryption algorithms, but they work
differently
...
This allows for a more efficient encryption process, as the encryption can
be done in real-time
...


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
...
Still, they also have a higher risk of repeating patterns in the keystream, which
can lead to security vulnerabilities
...
The key must be changed after
a certain number of encrypted bits to prevent this
...
A key exchange algorithm is used v
...

A key exchange algorithm is a cryptographic technique used to exchange keys between two
parties securely
...
This
shared private key can then encrypt and decrypt messages between the parties
...
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
...
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
...
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
...


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 exchange algorithm is widely used in secure communication protocols such as
IPSec, SSH, and SSL/TLS
...
The algorithm involves
the generation of a pair of public and private keys, which are exchanged between the two
parties
...
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, making it difficult for an attacker to factorize the large composite numbers
and obtain the private key
...
The Advanced Encryption Standard (AES) is a widely used symmetric encryption algorithm
considered highly secure
...
The AES algorithm
uses a fixed-size block of 128 bits and can use key sizes of 128, 192, or 256 bits
...
The US government adopted it in 2001 as the standard for encrypting
sensitive information, and organizations and individuals now use it worldwide to protect their
data
...
The algorithm applies a series of mathematical operations, known as rounds, to the
plaintext using a secret key
...
The larger the key size, the more secure the encryption and the more required
computation
...
A block cipher encrypts data in fixed-size blocks, typically 128 bits, and the critical
program ensures that the encryption key is changed for each block, making it more difficult for
an attacker to decrypt the data
...


In summary, The Advanced Encryption Standard (AES) is a widely used symmetric encryption
algorithm considered highly secure
...
The AES
algorithm uses a fixed-size block of 128 bits and can use key sizes of 128, 192, or 256 bits
...
Additionally, the algorithm has been
subject to extensive analysis and has yet to be broken, making it a widely accepted standard for
encryption
...
A Public Key Infrastructure (PKI) is a system that manages the issuance, revocation, and
distribution of digital certificates
...
A PKI is necessary because it provides
a secure method of verifying the identity of a party and can be used to establish secure
communication and e-commerce transactions
...
The PKI combines hardware, software, policies, and procedures to

create, manage, distribute, store, revoke and validate digital certificates
...


A PKI is necessary because it provides a secure method of verifying the identity of a party
...
When a user attempts to
communicate with another party over a network, the PKI can be used to verify the other party’s
identity before establishing a secure connection
...


The PKI also includes a certificate authority (CA), a trusted third party that issues digital
certificates to individuals and organizations
...


In summary, A Public Key Infrastructure (PKI) is a system that manages the issuance, revocation,
and distribution of digital certificates
...
A PKI is necessary because it
provides a secure method of verifying the identity of a party, which is essential for secure
communication and e-commerce transactions
...


15
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It is kept confidential and should only be known to the owner
...
The public key can encrypt data that the owner of the corresponding private key can
only decrypt
...
The private key is a secret value that is used to decrypt information
that has been encrypted with the corresponding public key
...
It is used to decrypt the encrypted data with the public key
...
It is used to encrypt the data that is intended for the owner of the private key
...
This ensures that only the intended recipient can read the data
...
This
allows for secure communication and data exchange, as the private key is kept confidential, and
only the owner can access it
...
In summary, A private key is a secret value encrypted with the corresponding public
key; it is kept confidential and should only be known to the owner
...


16
...
A digital envelope aims to ensure the data's confidentiality and integrity
...

A digital envelope is a method of encrypting data, such as a message, using a combination of
symmetric and asymmetric encryption algorithms
...


The symmetric encryption algorithm is used to encrypt the data, such as a message, this
algorithm is fast and efficient, but it requires the same key for encryption and decryption, which
can be a security vulnerability if the key falls into the wrong hands
...


The resulting ciphertext and the symmetric key are combined and encrypted using an
asymmetric encryption algorithm, such as RSA
...


The digital envelope method provides an additional layer of security compared to symmetric
encryption
...
Because the
symmetric key is encrypted using the recipient's public key, it eliminates the need for a secure
key distribution mechanism
...


In summary, A digital envelope is a method of encrypting data, such as a message, using a
combination of symmetric and asymmetric encryption algorithms
...

This ensures that only the intended recipient, who holds the corresponding private key, can
decrypt the data and read the message
...
The Elliptic Curve Digital Signature Algorithm (ECDSA) is a widely used digital signature
algorithm based on elliptic curves' mathematical properties
...
The private key is used to create the digital
signature, which can then be verified using the corresponding public key
...

The Elliptic Curve Digital Signature Algorithm (ECDSA) is a widely used digital signature
algorithm based on elliptic curves' mathematical properties
...


Like RSA, ECDSA uses public and private keys to create a digital signature
...
The process of creating a digital signature using ECDSA is similar to the operation of
signing a document
...


The security of the ECDSA algorithm is based on the difficulty of solving the discrete logarithm
problem in the group of points on an elliptic curve
...
It is tough to
determine the private key from the public key, making it difficult for an attacker to forge a
digital signature
...
It uses a pair of public and private
keys, similar to RSA, to create a digital signature
...
The security of the
ECDSA algorithm is based on the difficulty of solving the discrete logarithm problem in the
group of points on an elliptic curve, which is considered computationally infeasible, making it
difficult for an attacker to forge a digital signature
...
A digital signature verifies the authenticity and integrity of digital information, such as an
electronic document
...
The resulting digital signature can then be verified using the
corresponding public key
...
It is created by applying a specific mathematical
algorithm to show data and a secret key
...

The main difference between the two is that Digital Signature is typically used to ensure the
authenticity and integrity of the message’s sender
...

A digital signature verifies the authenticity and integrity of digital information, such as an
electronic document
...
The resulting digital signature can then be

verified using the corresponding public key
...


A MAC (Message Authentication Code) is a short piece of information used to authenticate a
message and provide integrity assurance
...
The resulting MAC value can be sent
along with the message and verified by the receiver using the same algorithm and the shared
private key
...


The main difference between a digital signature and a MAC is that a digital signature is typically
used to ensure the authenticity and integrity of the message’s sender
...
A digital signature uses public key cryptography
and a pair of public and private keys to create a digital signature, while a MAC uses a shared
secret key
...


In summary, A digital signature verifies the authenticity and integrity of digital information,
such as an electronic document
...
The resulting digital signature can then be verified using
the corresponding public key
...
It is created by
applying a specific mathematical algorithm to show data and a secret key
...
In contrast, MAC is used to ensure the integrity of the
message
...
A digital signature can be verified by using the corresponding public key to decrypt the
digital signature and compare it to the original data
...

A one-time pad is a symmetric encryption algorithm that uses a truly random key that is the
same length as the plaintext
...
On the other
hand, a stream cipher uses a pseudorandom keystream to encrypt the plaintext
...
At the same time, a
stream cipher can be vulnerable to keystream repetition
...
It is created by applying a mathematical algorithm, such as RSA or ECDSA,
to the data to be signed, along with a private key
...
The
receiver can check if the decrypted signature matches the original data; if it does, it confirms
the authenticity and integrity of the message and the sender
...
The key is used only once and is then discarded
...


On the other hand, a stream cipher uses a pseudorandom keystream to encrypt the plaintext
...


The main difference between the two is that the One-time pad is considered completely
unbreakable as long as the key is truly random and used only once
...


20
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The key is used only once and is then discarded
...
Since the key is truly random and used only once, the resulting
ciphertext is entirely arbitrary and unbreakable as long as the key remains secret
...
A
pseudorandom keystream is generated by a deterministic algorithm, which means that the
same keystream can be generated multiple times
...
The security of

a stream cipher relies on the key being kept secret and the keystream being unpredictable
...


In summary, the main difference between a one-time pad and a stream cipher is that a onetime pad is considered completely unbreakable as long as the key is truly random and used only
once
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