Question 1

digestpp vs OpenSSL for C++ hashing?

Accepted Answer

digestpp offers a header-only, modern C++ API with no dependencies, but OpenSSL provides better performance with SIMD optimizations and broader ecosystem support. Choose digestpp for simplicity and integration ease, OpenSSL for speed and maturity.

Question 2

How to hash a file with digestpp?

Accepted Answer

Use std::ifstream with the absorb() method, e.g., digestpp::sha256().absorb(file).hexdigest(). The library directly reads binary streams, making file hashing straightforward without manual buffering.

Question 3

Is digestpp thread-safe for multiple threads?

Accepted Answer

Distinct hasher instances are thread-safe, but sharing a single instance requires external synchronization. The README notes that modifying methods like absorb() on the same object from different threads is unsafe without locks.

Question 4

What's the difference between digest() and squeeze() in digestpp?

Accepted Answer

digest() is for hash functions with fixed or known output sizes and doesn't change state, while squeeze() is for XOFs to generate arbitrary-length outputs and updates state after each call. This is detailed in the library's design rationale.

Question 5

Can digestpp be used for password hashing with Argon2?

Accepted Answer

Yes, digestpp supports BLAKE2b with dynamic output sizes, which is often used in Argon2 implementations. However, you'd need to implement Argon2 yourself or combine it with other libraries, as digestpp only provides the hashing primitives.

Question 6

How to specify output size at compile-time vs runtime?

Accepted Answer

Use template parameters for compile-time, e.g., static_size::blake2b<256>(), or constructor arguments for runtime, e.g., blake2b(256). The README explains this flexibility for algorithms like BLAKE2 and SHA-512.

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