Excerpt
SHA-256 is widely used for secure hashing operations like password storage. This post looks at whether brute force attacks are feasible against SHA-256 given its 256-bit output space and the computational difficulty of trying all combinations.
Introduction
SHA-256 is a cryptographic hash algorithm that produces a 256-bit hash value. It is widely used for password hashing and digital signatures. Brute force attacks involve trying every possible combination in order to crack passwords and encryption. But can SHA-256 be brute forced? Let’s take a deeper look.
Understanding SHA-256
SHA-256 was designed by the NSA and published in 2001. It produces a fixed length 256-bit (32 byte) hash value. Some key properties of SHA-256 are:
- One-way function - it is not possible to reverse the hashing process to recover the original input.
- Small change in input leads to completely different hash - even a single bit change in the input drastically changes the hash.
- Highly unlikely for two different inputs to produce the same hash - known as collision resistance.
These make SHA-256 highly secure and resistant to collisions. It is suitable for password hashing and digital signatures.
The Process of Brute Force Attacks
Brute force attacks involve systematically trying every possible combination of inputs to crack passwords and encryption. The steps are:
- Try every possible combination as input.
- Calculate the hash for each input.
- Compare the calculated hash to the target hash.
- If a match is found, the input is the password/key.
The computational power and time required grows exponentially as the key space increases. For a 256-bit key, trying all combinations would take billions of years with current technology.
Breaking SHA-256 with Brute Force
SHA-256 has a 256-bit hash output. This means there are 2^256 or 115 quattuorvigintillion possible hash values. To brute force SHA-256, all these combinations have to be calculated and compared to the target hash.
With the Bitcoin network currently performing over 100 quintillion SHA-256 computations per second, it would still take more than a billion times the age of the universe to brute force a single SHA-256 hash.
Clearly, brute forcing SHA-256 is not practically feasible with current technology.
Difficulty of Brute Forcing SHA-256
There are a few reasons why SHA-256 is extremely resistant to brute force attacks:
Large keyspace - With 2^256 possibilities, the keyspace of SHA-256 is enormous by design. This makes trying all combinations practically impossible.
Rapidly advancing technology doesn’t help much - Computing power has increased exponentially over the past decades. But so has the difficulty level of brute forcing algorithms. Even with quantum computing, brute forcing SHA-256 remains infeasible.
Specialized hardware not effective - Purpose-built hardware for Bitcoin mining shows specialized equipment provides only a modest increase in brute forcing capability.
Overall, the design of SHA-256 ensures that brute force attacks are futile even with major advances in technology.
Other Methods for Breaking SHA-256
While brute force is not feasible, cryptanalysts have studied other types of attacks on SHA-256:
- Collision attacks - Finding two inputs with the same hash is the most promising attack but still extremely difficult in practice.
- Analytical attacks - Finding mathematical weaknesses in the algorithm to enable shortcuts to finding collisions. No analytical weaknesses have been found.
But these attacks are still theoretical and highly improbable with current research. Brute force remains the only directly applicable attack, though not practically viable.
Conclusion
In summary, SHA-256 is designed to be highly resilient against brute force attacks. Its 256-bit output space ensures trying all combinations is computationally infeasible now and for the foreseeable future. While alternative cryptanalytic attacks exist, brute force remains the only direct attack vector. Given its strength against brute forcing, SHA-256 provides highly reliable protection for sensitive data in cryptography and digital security.
