Add BigInt::square plus a speed test for BigInt multiply

3 files changed, 25 insertions, 8 deletions

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
@@ -252,6 +252,12 @@ 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
      * @param y_size length of y in 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;
    }