Key derives a key from the password, salt, and cost parameters, returning a byte slice of length keyLen that can be used as cryptographic key.

N is a CPU/memory cost parameter, which must be a power of two greater than 1. r and p must satisfy r * p < 2³⁰. If the parameters do not satisfy the limits, the function returns a nil byte slice and an error.

For example, you can get a derived key for e.g. AES-256 (which needs a 32-byte key) by doing:

dk := scrypt.Key([]byte("some password"), salt, 16384, 8, 1, 32)

The recommended parameters for interactive logins as of 2009 are N=16384, r=8, p=1. They should be increased as memory latency and CPU parallelism increases. Remember to get a good random salt.

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