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 security needs of any business.
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. If a company or business wants to hire a cryptographer, either full-time or on a contract basis, these questions can also be used in an interview.
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As an aspiring developer preparing for technical interviews, you need to be well-versed in various technologies and concepts related to building secure applications One crucial aspect that frequently comes up is bcrypt – mentioned 15 times across the content.
Bcrypt is a robust password hashing function that is widely used to protect sensitive user information Given its importance, interviewers often test candidates on their bcrypt knowledge through a mix of theoretical and practical questions. Mastering common bcrypt interview questions will boost your chances of landing your dream developer role
This comprehensive guide provides an overview of bcrypt and the key topics to expect in an interview Let’s get started!
What is bcrypt and why is it used?
The first fundamental bcrypt interview question you may encounter is an explanation of what bcrypt is and its purpose.
Bcrypt is an adaptive password hashing algorithm based on the Blowfish cipher. It introduces a configurable computational cost, making the function slower and more resource intensive. This prevents brute force attacks even as computing power increases.
Key reasons why bcrypt is widely used for password hashing:
- Built-in salting to thwart rainbow table attacks
- Adaptive cost factor to resist brute force attempts by increasing compute time
- Specifically designed for hashing passwords unlike faster algorithms like MD5
- Resilient against GPU cracking attempts due to memory hardness
Understanding bcrypt’s core principles will help you explain its significance as a password security tool.
How does bcrypt work?
Interviewers commonly ask candidates to walk through bcrypt’s underlying process. Here are the key steps:
- A random salt is generated for each password.
- The salt is combined with the password and fed into the bcrypt algorithm.
- The algorithm outputs a hash value along with the embedded salt. This hash is stored for later verification.
- During login, the user-entered password is salted and hashed again using the same process.
- The two hash values are compared. If equal, the user is authenticated.
The salting and slow hashing ensure brute force and rainbow table attacks are ineffective.
What is the importance of salting passwords?
You should be able to articulate the role of salting and its significance. Salting refers to combining random data (called salt) with the original password before hashing it.
Key benefits of salting:
- Makes rainbow table attacks infeasible since tables must be computed for each salt
- Even duplicate passwords result in unique hashes due to different salts
- Salts are randomly generated to prevent salt reuse across systems
Bcrypt handles salting internally so developers don’t have to implement it manually.
How does the cost factor enhance security?
Bcrypt’s cost factor or work factor is another common interview topic. It determines the computational expense of the hash by controlling the number of internal iterations.
A higher cost factor means:
- Each hashing operation takes more time
- Brute forcing passwords requires more resources
- Resists cracking attempts as hardware improves over time
The cost factor can be increased seamlessly to maintain security. However, it impacts hash generation performance and must be tuned appropriately.
What are bcrypt’s limitations?
You may be asked about bcrypt’s drawbacks compared to newer algorithms like Argon2. Key limitations include:
- Password length limit of 72 characters
- Not memory hard – vulnerable to ASIC/FPGA attacks
- Not parallelizable for multi-core systems
- Slower at higher cost factors impacting response times
While bcrypt remains secure for most applications, these limitations have led to newer password hashing schemes.
How would you implement bcrypt correctly?
For this practical question, focus on:
- Never implementing your own cryptographic primitives
- Using tested libraries like passlib for Python instead of coding from scratch
- Properly handling user input – watch for null bytes truncating passwords
- Storing only the hash and salt – never plaintext passwords
- Updating cost factor and rehashing as hardware capabilities increase
Demonstrate awareness of common pitfalls like logging hashed passwords or failing to salt them.
What would you test to ensure bcrypt effectiveness?
Some ways to test your bcrypt implementation:
- Unit tests to validate password hashing and salting functions
- Penetration testing using password cracking tools to find weaknesses
- Load testing to ensure performance at scale under heavy loads
- Security review of codebase for plaintext password leaks
- Input validation to protect against null byte injection attacks
Share examples of tools like hashcat, Burp Suite etc. to show your technical knowledge.
Key Takeaways
- Bcrypt is a secure password hashing algorithm using salting and adjustable cost factors
- Know how salting, hashing and key derivation take place
- Explain the role of cost factors in preventing brute force attacks
- Discuss limitations and alternatives like Argon2 where appropriate
- Demonstrate ability to implement bcrypt properly using best practices
- Share techniques to test effectiveness of your bcrypt implementation
What is the Public Key Infrastructure (PKI)?
Since the public key is so important for encrypting and decrypting ciphertext messages between senders and receivers, as well as for its public role in communication in general, a lot of work and research has gone into building an infrastructure that makes the process of making and sending keys much safer and more reliable.
The “Public Key Infrastructure,” or “PKI,” is a very advanced form of asymmetric cryptography. The basic premise of PKI is to help create, organize, store, distribute and maintain the public keys.
What are the disadvantages of asymmetric cryptography?
Asymmetric cryptography has some good points, but it also has a very big problem: it is two to three times slower than symmetric cryptography. This is primarily because of the multiple parties and multiple keys which are involved.
Password Storage Tier List: encryption, hashing, salting, bcrypt, and beyond
FAQ
What is the purpose of bcrypt?
Which algorithm is used in bcrypt?
Is bcrypt secure for passwords?
Is bcrypt outdated?
What is bcrypt cipher?
Bcrypt is a password-hashing algorithm designed to be slow and computationally expensive. Its primary purpose is to resist brute-force attacks by slowing the hashing process. Bcrypt employs the Blowfish cipher to convert plaintext passwords into a fixed-length string of characters called a hash. This hash is then stored in the database.
How to use bcrypt?
To use bcrypt, you’ll need to import bcrypt module, After that the bcrypt.hashpw () function takes 2 arguments: A string (bytes) and Salt. Salt is random data used in the hashing function. Let’s hash a password and print it in the following examples.
How does bcrypt work for password storage?
Bcrypt is a password-hashing function that relies heavily on accesses to a table which is constantly altered throughout the algorithm execution. This makes it slower on a GPU, where memory is shared and all cores compete for control of the internal memory bus. It is often recommended by security experts for password storage due to its security benefits.
How does bcrypt verify a password in JavaScript?
Bcrypt automatically retrieves the salt value from the hash and applies the hashing algorithm to the provided password, allowing for a secure comparison. Example: Let’s assume Alice tries to log in to Hops-Haven. We can verify her password using the following code snippet in JavaScript: const storedHash = “”;
