256bits

256 bits is a unit of information equal to 256 binary digits. A 256-bit value can represent 2^256 distinct states, which is roughly 1.16 × 10^77. Such a large space underpins the strong security assumptions behind many modern cryptographic systems and fixed-size data representations.

In practice, 256-bit lengths are commonly used for cryptographic keys, hashes, and identifiers. AES-256 uses a 256-bit symmetric key, providing a very large key space to deter brute-force attempts. Hash functions such as SHA-256 produce a 256-bit output, offering preimage resistance up to about 2^256 operations and, due to the birthday bound, collision resistance on the order of 2^128. Elliptic curve cryptography often employs 256-bit curves (for example, secp256k1) that aim for roughly 128-bit security against classical attacks.

A 256-bit quantity is typically stored as 32 bytes of data. Representations in software commonly use big-endian or little-endian byte order, depending on the context, with 256-bit values appearing in keys, hashes, and unique identifiers.

Security considerations note that, while 256-bit keys are currently regarded as infeasible to break with classical computation, advances in quantum computing could reduce the effective security level. Under Grover’s algorithm, a 256-bit key’s security could be reduced to approximately 2^128 quantum operations, influencing future cryptographic standards and risk assessments.

Beyond cryptography, 256-bit widths also appear in digital addressing, random number generation, and various protocol specifications where fixed-size identifiers are desirable.