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randombit / botan / 19308433318

12 Nov 2025 06:51PM UTC coverage: 91.956% (+1.3%) from 90.624%
19308433318

Pull #5153

github

web-flow
Merge 84439abca into e78c62c39
Pull Request #5153: Add std::array support to BigInt::serialize function

102125 of 111058 relevant lines covered (91.96%)

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77.45
/src/lib/pbkdf/scrypt/scrypt.cpp
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/**
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* (C) 2018 Jack Lloyd
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* (C) 2018 Ribose Inc
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#include <botan/scrypt.h>
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#include <botan/exceptn.h>
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#include <botan/pbkdf2.h>
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#include <botan/internal/bit_ops.h>
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#include <botan/internal/fmt.h>
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#include <botan/internal/loadstor.h>
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#include <botan/internal/mem_utils.h>
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#include <botan/internal/salsa20.h>
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#include <botan/internal/time_utils.h>
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namespace Botan {
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namespace {
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size_t scrypt_memory_usage(size_t N, size_t r, size_t p) {
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   return 128 * r * (N + p);
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}
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}  // namespace
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std::string Scrypt_Family::name() const {
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   return "Scrypt";
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}
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std::unique_ptr<PasswordHash> Scrypt_Family::default_params() const {
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   return std::make_unique<Scrypt>(32768, 8, 1);
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}
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std::unique_ptr<PasswordHash> Scrypt_Family::tune(size_t output_length,
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                                                  std::chrono::milliseconds msec,
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                                                  size_t max_memory_usage_mb,
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                                                  std::chrono::milliseconds tune_time) const {
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   BOTAN_UNUSED(output_length);
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   /*
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   * Some rough relations between scrypt parameters and runtime.
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   * Denote here by stime(N,r,p) the msec it takes to run scrypt.
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   *
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   * Empirically for smaller sizes:
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   * stime(N,8*r,p) / stime(N,r,p) is ~ 6-7
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   * stime(N,r,8*p) / stime(N,r,8*p) is ~ 7
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   * stime(2*N,r,p) / stime(N,r,p) is ~ 2
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   *
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   * Compute stime(8192,1,1) as baseline and extrapolate
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   */
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   // This is zero if max_memory_usage_mb == 0 (unbounded)
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   const size_t max_memory_usage = max_memory_usage_mb * 1024 * 1024;
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   // Starting parameters
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   size_t N = 8 * 1024;
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   size_t r = 1;
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   size_t p = 1;
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   auto pwdhash = this->from_params(N, r, p);
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   const uint64_t measured_time = measure_cost(tune_time, [&]() {
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      uint8_t output[32] = {0};
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      pwdhash->derive_key(output, sizeof(output), "test", 4, nullptr, 0);
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   });
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   const uint64_t target_nsec = msec.count() * static_cast<uint64_t>(1000000);
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   uint64_t est_nsec = measured_time;
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   // In below code we invoke scrypt_memory_usage with p == 0 as p contributes
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   // (very slightly) to memory consumption, but N is the driving factor.
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   // Including p leads to using an N half as large as what the user would expect.
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   // First increase r by 8x if possible
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   if(max_memory_usage == 0 || scrypt_memory_usage(N, r * 8, 0) <= max_memory_usage) {
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      if(target_nsec / est_nsec >= 5) {
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         r *= 8;
×
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         est_nsec *= 5;
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      }
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   }
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   // Now double N as many times as we can
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   while(max_memory_usage == 0 || scrypt_memory_usage(N * 2, r, 0) <= max_memory_usage) {
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      if(target_nsec / est_nsec >= 2) {
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         N *= 2;
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         est_nsec *= 2;
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      } else {
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         break;
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      }
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   }
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   // If we have extra runtime budget, increment p
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   if(target_nsec / est_nsec >= 2) {
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      p *= std::min<size_t>(1024, static_cast<size_t>(target_nsec / est_nsec));
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   }
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   return std::make_unique<Scrypt>(N, r, p);
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}
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std::unique_ptr<PasswordHash> Scrypt_Family::from_params(size_t N, size_t r, size_t p) const {
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   return std::make_unique<Scrypt>(N, r, p);
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}
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std::unique_ptr<PasswordHash> Scrypt_Family::from_iterations(size_t iter) const {
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   const size_t r = 8;
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   const size_t p = 1;
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   size_t N = 8192;
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   if(iter > 50000) {
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      N = 16384;
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   }
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   if(iter > 100000) {
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      N = 32768;
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   }
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   if(iter > 150000) {
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      N = 65536;
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   }
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   return std::make_unique<Scrypt>(N, r, p);
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}
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Scrypt::Scrypt(size_t N, size_t r, size_t p) : m_N(N), m_r(r), m_p(p) {
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   if(!is_power_of_2(N)) {
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      throw Invalid_Argument("Scrypt N parameter must be a power of 2");
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   }
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   if(p == 0 || p > 1024) {
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      throw Invalid_Argument("Invalid or unsupported scrypt p");
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   }
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   if(r == 0 || r > 256) {
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      throw Invalid_Argument("Invalid or unsupported scrypt r");
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   }
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   if(N < 1 || N > 4194304) {
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      throw Invalid_Argument("Invalid or unsupported scrypt N");
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   }
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}
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std::string Scrypt::to_string() const {
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   return fmt("Scrypt({},{},{})", m_N, m_r, m_p);
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}
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size_t Scrypt::total_memory_usage() const {
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   const size_t N = memory_param();
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   const size_t p = parallelism();
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   const size_t r = iterations();
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   return scrypt_memory_usage(N, r, p);
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}
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namespace {
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void scryptBlockMix(size_t r, uint8_t* B, uint8_t* Y) {
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   uint32_t B32[16];
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   secure_vector<uint8_t> X(64);
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   copy_mem(X.data(), &B[(2 * r - 1) * 64], 64);
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   for(size_t i = 0; i != 2 * r; i++) {
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      xor_buf(X.data(), &B[64 * i], 64);
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      load_le<uint32_t>(B32, X.data(), 16);
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      Salsa20::salsa_core(X.data(), B32, 8);
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      copy_mem(&Y[64 * i], X.data(), 64);
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   }
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   for(size_t i = 0; i < r; ++i) {
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      copy_mem(&B[i * 64], &Y[(i * 2) * 64], 64);
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   }
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   for(size_t i = 0; i < r; ++i) {
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      copy_mem(&B[(i + r) * 64], &Y[(i * 2 + 1) * 64], 64);
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   }
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}
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void scryptROMmix(size_t r, size_t N, uint8_t* B, secure_vector<uint8_t>& V) {
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   const size_t S = 128 * r;
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   for(size_t i = 0; i != N; ++i) {
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      copy_mem(&V[S * i], B, S);
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      scryptBlockMix(r, B, &V[N * S]);
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   }
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   for(size_t i = 0; i != N; ++i) {
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      // compiler doesn't know here that N is power of 2
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      const size_t j = load_le<uint32_t>(&B[(2 * r - 1) * 64], 0) & (N - 1);
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      xor_buf(B, &V[j * S], S);
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      scryptBlockMix(r, B, &V[N * S]);
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   }
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}
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}  // namespace
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void Scrypt::derive_key(uint8_t output[],
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                        size_t output_len,
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                        const char* password,
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                        size_t password_len,
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                        const uint8_t salt[],
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                        size_t salt_len) const {
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   const size_t N = memory_param();
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   const size_t p = parallelism();
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   const size_t r = iterations();
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   const size_t S = 128 * r;
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   secure_vector<uint8_t> B(p * S);
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   // temp space
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   secure_vector<uint8_t> V((N + 1) * S);
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   auto hmac_sha256 = MessageAuthenticationCode::create_or_throw("HMAC(SHA-256)");
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   try {
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      hmac_sha256->set_key(as_span_of_bytes(password, password_len));
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   } catch(Invalid_Key_Length&) {
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      throw Invalid_Argument("Scrypt cannot accept passphrases of the provided length");
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   }
×
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   pbkdf2(*hmac_sha256, B.data(), B.size(), salt, salt_len, 1);
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   // these can be parallel
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   for(size_t i = 0; i != p; ++i) {
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      scryptROMmix(r, N, &B[128 * r * i], V);
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   }
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   pbkdf2(*hmac_sha256, output, output_len, B.data(), B.size(), 1);
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}
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}  // namespace Botan
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