hashlib_PBKDF2(const uint8_t* password, size_t plen, uint8_t* out, const uint8_t* salt, size_t slen, uint24_t iter_count, size_t keylen){
    HASH = sha256
    DK = T(i) for i in 0 => (keylen/HASH), concat
    T(i) = F(password, salt, c, i) = U1 xor U2 xor ... xor Uc
        U1 = PRF(Password, Salt + INT_32_BE(i))
        U2 = PRF(Password, U1)
        ⋮
        Uc = PRF(Password, Uc−1)
}