From 0ca00cd6184a9c9e4d6a0dfc8a2488746ee22f23 Mon Sep 17 00:00:00 2001
From: Jack Lloyd <jack@randombit.net>
Date: Sun, 8 Apr 2018 19:21:35 -0400
Subject: Add BigInt::square plus a speed test for BigInt multiply

---
 src/cli/speed.cpp                      | 47 ++++++++++++++++++++++++++++++++++
 src/lib/math/bigint/big_ops2.cpp       | 16 ++++++++++++
 src/lib/math/bigint/bigint.h           |  6 +++++
 src/lib/math/numbertheory/mp_numth.cpp | 11 +++-----
 4 files changed, 72 insertions(+), 8 deletions(-)

diff --git a/src/cli/speed.cpp b/src/cli/speed.cpp
index afe75decc..b8397363f 100644
--- a/src/cli/speed.cpp
+++ b/src/cli/speed.cpp
@@ -23,6 +23,10 @@
 #include <botan/internal/os_utils.h>
 #include <botan/version.h>
 
+#if defined(BOTAN_HAS_BIGINT)
+   #include <botan/bigint.h>
+#endif
+
 #if defined(BOTAN_HAS_BLOCK_CIPHER)
    #include <botan/block_cipher.h>
 #endif
@@ -895,6 +899,13 @@ class Speed final : public Command
                }
 #endif
 
+#if defined(BOTAN_HAS_BIGINT)
+            else if(algo == "mp_mul")
+               {
+               bench_mp_mul(msec);
+               }
+#endif
+
 #if defined(BOTAN_HAS_NUMBERTHEORY)
             else if(algo == "random_prime")
                {
@@ -1428,6 +1439,42 @@ class Speed final : public Command
          }
 #endif
 
+#if defined(BOTAN_HAS_BIGINT)
+
+      void bench_mp_mul(const std::chrono::milliseconds runtime)
+         {
+         std::chrono::milliseconds runtime_per_size = runtime / 9;
+         for(size_t bits : { 256, 384, 512, 768, 1024, 1536, 2048, 3072, 4096 })
+            {
+            std::unique_ptr<Timer> mul_timer = make_timer("BigInt mul " + std::to_string(bits));
+            std::unique_ptr<Timer> sqr_timer = make_timer("BigInt sqr " + std::to_string(bits));
+
+            const Botan::BigInt y(rng(), bits);
+            Botan::secure_vector<Botan::word> ws;
+
+            while(mul_timer->under(runtime_per_size))
+               {
+               Botan::BigInt x(rng(), bits);
+
+               sqr_timer->start();
+               x.square(ws);
+               sqr_timer->stop();
+
+               x.mask_bits(bits);
+
+               mul_timer->start();
+               x.mul(y, ws);
+               mul_timer->stop();
+               }
+
+            record_result(mul_timer);
+            record_result(sqr_timer);
+            }
+
+         }
+
+#endif
+
 #if defined(BOTAN_HAS_DL_GROUP)
 
       void bench_modexp(const std::chrono::milliseconds runtime)
diff --git a/src/lib/math/bigint/big_ops2.cpp b/src/lib/math/bigint/big_ops2.cpp
index 9277834ba..eea6a8590 100644
--- a/src/lib/math/bigint/big_ops2.cpp
+++ b/src/lib/math/bigint/big_ops2.cpp
@@ -177,6 +177,22 @@ BigInt& BigInt::mul(const BigInt& y, secure_vector<word>& ws)
    return (*this);
    }
 
+BigInt& BigInt::square(secure_vector<word>& ws)
+   {
+   const size_t sw = sig_words();
+
+   secure_vector<word> z(2*sw);
+   ws.resize(z.size());
+
+   bigint_sqr(z.data(), z.size(),
+              data(), size(), sw,
+              ws.data(), ws.size());
+
+   swap_reg(z);
+
+   return (*this);
+   }
+
 BigInt& BigInt::operator*=(word y)
    {
    if(y == 0)
diff --git a/src/lib/math/bigint/bigint.h b/src/lib/math/bigint/bigint.h
index cb518e727..44177de96 100644
--- a/src/lib/math/bigint/bigint.h
+++ b/src/lib/math/bigint/bigint.h
@@ -251,6 +251,12 @@ class BOTAN_PUBLIC_API(2,0) BigInt final
      */
      BigInt& mul(const BigInt& y, secure_vector<word>& ws);
 
+     /**
+     * Square value of *this
+     * @param ws a temp workspace
+     */
+     BigInt& square(secure_vector<word>& ws);
+
      /**
      * Set *this to y - *this
      * @param y the BigInt to subtract from as a sequence of words
diff --git a/src/lib/math/numbertheory/mp_numth.cpp b/src/lib/math/numbertheory/mp_numth.cpp
index 5ad72cd47..eef641996 100644
--- a/src/lib/math/numbertheory/mp_numth.cpp
+++ b/src/lib/math/numbertheory/mp_numth.cpp
@@ -18,14 +18,9 @@ namespace Botan {
 */
 BigInt square(const BigInt& x)
    {
-   const size_t x_sw = x.sig_words();
-
-   BigInt z(BigInt::Positive, round_up(2*x_sw, 16));
-   secure_vector<word> workspace(z.size());
-
-   bigint_sqr(z.mutable_data(), z.size(),
-              x.data(), x.size(), x_sw,
-              workspace.data(), workspace.size());
+   BigInt z = x;
+   secure_vector<word> ws;
+   z.square(ws);
    return z;
    }
 
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