What is cryptography? How does it work? What is it used for? How can it be used to protect an organization’s private data and information? How can it be used to protect the lines of communication between a worker in another location and the company’s servers?
These are all questions that a well-trained cryptographer can answer. They know everything there is to know about this amazing part of cybersecurity, from how it works to how it can be best used to meet the needs of any organization’s security needs.
We will look at the thirty most common questions that you can ask an experienced cryptographer, ranging from what cryptography is all about to how it can be used in business. These types of questions can be broken into down into Level 1, Level 2 and Level 3 questions. These questions can also be used in an interview when a company or business wants to hire a cryptographer on a contract or full-time basis.
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Mastering bcrypt Interview Questions A Comprehensive Guide
In the realm of cybersecurity, understanding bcrypt, a robust password hashing algorithm, is not just beneficial, it’s essential. Whether you’re a budding developer or a seasoned software engineer, knowledge about secure handling of user credentials is paramount.
This guide covers a lot of commonly asked interview questions about bcrypt. It will give you the knowledge and confidence to ace your next IT and cybersecurity job interview.
1, What is bcrypt and why is it considered secure for password hashing?
Bcrypt, the brainchild of Niels Provos and David Mazières, is a password hashing function designed to safeguard sensitive user data. It utilizes the Blowfish cipher, incorporating adaptability by allowing updates to the logarithmic cost factor, which controls the computational expense of the hash function. This feature makes it resistant to brute force search attacks even with increasing computation power.
The security of bcrypt lies in its adaptive nature and slow speed. The cost factor can be changed, so as hardware gets better, the algorithm can become more complicated. This keeps people safe from new threats. Attackers are even less likely to try because it is naturally slow, making each attempt take longer and cost more.
2 How does bcrypt handle salting and why is this important?
Bcrypt incorporates salting in its hashing process to enhance security. It generates a random salt for each password and combines it with the password before applying the hash function. This unique salt is stored alongside the hashed password, allowing verification without needing to store the original password.
Salting is crucial as it prevents attackers from using precomputed tables of hashes (rainbow tables) to crack passwords Even if two users have identical passwords, their salts are different, resulting in distinct hashes Thus, an attacker must compute a new rainbow table for each salt, which is computationally expensive and time-consuming.
Moreover, bcrypt’s adaptive nature allows increasing computational cost over time by adjusting the work factor. As hardware improves this feature ensures that brute-force attacks remain impractical, providing long-term security.
3. Please explain the concept of bcrypt work factor and its role in password security.
Bcrypt work factor, also known as cost factor, is a key component in password security. It determines the computational complexity of the hashing process, thereby influencing the time taken to hash and verify passwords. A higher work factor increases the processing time exponentially, making brute-force attacks less feasible due to increased resource requirements. However, it’s crucial to balance this with usability; excessive delays can negatively impact user experience. The bcrypt algorithm automatically incorporates the work factor into generated hashes, allowing for future increase in security without altering stored data.
4. How does bcrypt compare to other hashing algorithms like MD5, SHA1, or SHA256?
Because it is adaptive and has a built-in salting mechanism, Bcrypt is better than MD5, SHA1, and SHA256. Salting prevents rainbow table attacks by adding unique data to each hash. Because Bcrypt is flexible, it can raise the cost of computation over time as hardware gets better. This keeps brute force attacks safe. But bcrypt is made just for hashing passwords, so it works better for this purpose than the others.
5. Can you explain the potential implications of a low work factor in bcrypt?.
A low work factor in bcrypt can lead to potential security risks. Bcrypt uses a work factor to determine the computational cost of hashing passwords, making it resistant to brute force attacks. A lower work factor means less time and resources are required to compute the hash, which makes it easier for an attacker to guess the password through brute force or rainbow table attacks. This compromises the security of user data. Conversely, a higher work factor increases the time and computational power needed to crack the password, enhancing security but at the expense of system performance. Therefore, choosing an appropriate work factor is crucial; it must be high enough to deter attacks yet not so high that it significantly impacts system performance.
6. How does bcrypt stand against rainbow table attacks and why?
Bcrypt is highly resistant to rainbow table attacks due to its unique design. Rainbow tables are precomputed tables for reversing cryptographic hash functions, primarily used in password cracking. Bcrypt thwarts this by incorporating a salt into the hashing process. A salt is random data that’s generated for each new user password. It’s combined with the password before the bcrypt function is applied. This means even if two users have the same password, their hashed outputs will be different due to differing salts. The use of unique salts per password makes it computationally impractical to create a useful rainbow table as one would need a separate table for each possible salt value. Furthermore, bcrypt is designed to be slow and computationally intensive, which further deters brute-force and rainbow table attacks by making them time-consuming and costly.
7. How would you implement a password reset feature in a system that uses bcrypt for password storage?
To implement a password reset feature in a bcrypt system, you’d first generate a unique token and associate it with the user’s account. This token is then sent to the user via email. When the user clicks on the link containing the token, they’re directed to a secure page where they can enter a new password. The new password is hashed using bcrypt and stored in place of the old one. It’s crucial that this process happens over a secure connection to prevent interception. Also, tokens should expire after a certain period for security reasons.
8. Can you explain what log rounds are in bcrypt? How do they relate to the security of hashed passwords?
Log rounds in bcrypt refer to the number of times the hashing algorithm is applied. It’s a parameter that determines the computational cost of the hash function, thereby influencing the time taken for each attempt at cracking the password.
The higher the log round value, the more iterations of the hashing process are performed, making it exponentially harder and time-consuming for an attacker to guess the hashed password through brute force or rainbow table attacks. This increased complexity enhances the security of hashed passwords as it deters attackers due to the significant amount of resources required.
However, there’s a trade-off between security and performance. Higher log rounds mean slower password verification processes, which could potentially degrade user experience if set too high. Therefore, choosing the appropriate log round value involves balancing these two aspects based on specific application requirements and threat models.
9. Explain the process involved in comparing a plaintext password with a hashed password in bcrypt.
Bcrypt is a password hashing function designed for security. When comparing a plaintext password with a hashed one, bcrypt follows several steps. Initially, the plaintext password is taken as input by the bcrypt algorithm. This algorithm then generates a salt, which is random data used as an additional input to the hash function. The salt and plaintext password are combined and processed through the bcrypt hash function, producing a unique hashed output.
This output is stored in the system’s database along with the generated salt. When a user attempts to log in, the entered password undergoes the same process: it’s combined with the stored salt and passed through the bcrypt function. The resulting hash is compared with the stored hash. If they match, access is granted; if not, access is denied.
10. What is the process for handling bcrypt’s salts when migrating users to a new system?
When migrating users to a new system, bcrypt’s salts are handled through the following process:
Firstly, you must ensure that the original salt used for each user is stored securely. This is crucial as it is needed to verify passwords on the new system.
Next, during migration, each user’s password should be rehashed using the same salt and the bcrypt algorithm. The resulting hash should match the one in the old system, confirming successful migration.
In case of changing hashing algorithms, the best practice is to use a two-step approach. Initially, continue using bcrypt with the old salt. When users log in, capture their plaintext password, hash it with the new algorithm and store this alongside the bcrypt hash. Over time, as users log in, their hashes will be updated. Users who don’t log in within a certain period can be prompted to reset their password.
11. Discuss the relationship between bcrypt and Blowfish cipher, from which bcrypt is derived.
Bcrypt is a password hashing function derived from the Blowfish cipher. The relationship between bcrypt and Blowfish lies in their shared cryptographic structure, with bcrypt being an adaptation of the Blowfish keying schedule. Bcrypt incorporates a salt to protect against rainbow table attacks and uses an adaptive cost factor for controlling the amount of processing needed to hash and check passwords, which helps resist brute-force search attacks. This makes it more secure than its predecessor.
12. How does bcrypt respond to time-memory trade-off attacks?
Bcrypt is designed to be resistant to time-memory trade-off attacks. It achieves this by using a salt and an adaptive cost factor. The salt ensures that each user’s hash is unique, preventing pre-computation of hashes for attack purposes. The adaptive cost factor allows the computation time to increase with hardware capabilities, making brute force attacks more difficult as technology advances. This combination makes bcrypt highly resilient against these types of attacks.
13. If given a choice between using bcrypt and scrypt, which one would you choose and why?
I would choose bcrypt for its balance of security and efficiency. Bcrypt is a password hashing function designed by Niels Provos and David Mazières, based on the Blowfish cipher. It incorporates a salt to protect against rainbow table attacks and iterates over a key setup 2^work_factor times.
Scrypt, while also secure, requires more memory resources which can be an issue in constrained environments. Its high memory usage makes it
What are the key differences between asymmetric and symmetric cryptography?
With symmetric cryptography, the complete secrecy of the key must be assured. Whereas asymmetric cryptography requires only half of the secrecy, namely that of the private key (sk).
Secondly, in symmetric cryptography, the ciphertext is encrypted and decrypted using the same secret key. In asymmetric cryptography, on the other hand, the ciphertext is encrypted and decrypted using two different keys, called the public and private keys.
What is cipher block chaining?
The initialization vectors are part of a larger process known as cipher block chaining, or CBC. Within this methodology, multiple loops of encryption are created in order to further totally scramble the ciphertext.
Here is the how the process works:
- The Initialization Vector is created first
- It is a common mathematical operation to check if the bits in two strings of data match or not. The first Initialization Vector is XORed with the first block of ciphertext data. XOR stands for “exclusive OR.”
- A second level of encryption is added to the first piece of data that has been XORed.
- This process keeps going until all the ciphertext blocks have been XORed and wrapped in another layer of encryption.
This is how cipher block chaining gets its title. For example, steps 1–4 start the first loop or chain. The second loop or chain is then started, and so on, until this method has fully analyzed and encrypted the ciphertext.
Bcrypt & Password Security – An Introduction
FAQ
What is bcrypt used for?
Why is bcrypt so secure?
What level of encryption is bcrypt?
What are the implementations of bcrypt?
