3 files changed, 23 insertions, 6 deletions
diff --git a/src/pubkey/dsa/dsa.cpp b/src/pubkey/dsa/dsa.cpp
index feac712b8..2b9a73015 100644
--- a/src/pubkey/dsa/dsa.cpp
+++ b/src/pubkey/dsa/dsa.cpp
@@ -8,6 +8,7 @@
 #include <botan/dsa.h>
 #include <botan/numthry.h>
 #include <botan/keypair.h>
+#include <future>
 
 namespace Botan {
 
@@ -95,10 +96,14 @@ DSA_Signature_Operation::sign(const byte msg[], u32bit msg_len,
       k.randomize(rng, q.bits());
    while(k >= q);
 
+   auto future_r = std::async(std::launch::async,
+                              [&]() { return mod_q.reduce(powermod_g_p(k)); });
+
    BigInt i(msg, msg_len);
 
-   BigInt r = mod_q.reduce(powermod_g_p(k));
-   BigInt s = mod_q.multiply(inverse_mod(k, q), mul_add(x, r, i));
+   BigInt s = inverse_mod(k, q);
+   BigInt r = future_r.get();
+   s = mod_q.multiply(s, mul_add(x, r, i));
 
    if(r.is_zero() || s.is_zero())
       throw Internal_Error("DSA signature gen failure: r or s was zero");
@@ -134,8 +139,14 @@ bool DSA_Verification_Operation::verify(const byte msg[], u32bit msg_len,
       return false;
 
    s = inverse_mod(s, q);
-   s = mod_p.multiply(powermod_g_p(mod_q.multiply(s, i)),
-                      powermod_y_p(mod_q.multiply(s, r)));
+
+   auto future_s_i = std::async(std::launch::async,
+      [&]() { return powermod_g_p(mod_q.multiply(s, i)); });
+
+   BigInt s_r = powermod_y_p(mod_q.multiply(s, r));
+   BigInt s_i = future_s_i.get();
+
+   s = mod_p.multiply(s_i, s_r);
 
    return (mod_q.reduce(s) == r);
    }
diff --git a/src/pubkey/nr/nr.cpp b/src/pubkey/nr/nr.cpp
index cf59615da..440fa22e4 100644
--- a/src/pubkey/nr/nr.cpp
+++ b/src/pubkey/nr/nr.cpp
@@ -8,6 +8,7 @@
 #include <botan/nr.h>
 #include <botan/numthry.h>
 #include <botan/keypair.h>
+#include <future>
 
 namespace Botan {
 
@@ -143,7 +144,10 @@ NR_Verification_Operation::verify_mr(const byte msg[], u32bit msg_len)
    if(c.is_zero() || c >= q || d >= q)
       throw Invalid_Argument("NR verification: Invalid signature");
 
-   BigInt i = mod_p.multiply(powermod_g_p(d), powermod_y_p(c));
+   auto future_y_c = std::async(std::launch::async, powermod_y_p, c);
+   BigInt g_d = powermod_g_p(d);
+
+   BigInt i = mod_p.multiply(g_d, future_y_c.get());
    return BigInt::encode(mod_q.reduce(c - i));
    }
 
diff --git a/src/pubkey/rsa/rsa.cpp b/src/pubkey/rsa/rsa.cpp
index 200e92821..e27b2056d 100644
--- a/src/pubkey/rsa/rsa.cpp
+++ b/src/pubkey/rsa/rsa.cpp
@@ -9,6 +9,7 @@
 #include <botan/parsing.h>
 #include <botan/numthry.h>
 #include <botan/keypair.h>
+#include <future>
 
 namespace Botan {
 
@@ -89,8 +90,9 @@ BigInt RSA_Private_Operation::private_op(const BigInt& m) const
    if(m >= n)
       throw Invalid_Argument("RSA private op - input is too large");
 
-   BigInt j1 = powermod_d1_p(m);
+   auto future_j1 = std::async(std::launch::async, powermod_d1_p, m);
    BigInt j2 = powermod_d2_q(m);
+   BigInt j1 = future_j1.get();
 
    j1 = mod_p.reduce(sub_mul(j1, j2, c));