Alter one of the constructors of DL_Group to take a parameter specifying

how big q should be.

Add FIPS 186-3 DSA parameter generation, this allows for generating larger
(2048 and 3072 bit) DSA keys. At this time there do not seem to be official
test vectors for 186-3, and I have not checked against other implementations.
Tests will be constructed using the latest OpenSSL snapshot.

1 files changed, 10 insertions, 5 deletions

diff --git a/src/dl_group.cpp b/src/dl_group.cpp
index 78a2952be..9d50458dd 100644
--- a/src/dl_group.cpp
+++ b/src/dl_group.cpp
@@ -35,7 +35,7 @@ DL_Group::DL_Group(const std::string& type)
 /*************************************************
 * DL_Group Constructor                           *
 *************************************************/
-DL_Group::DL_Group(u32bit pbits, PrimeType type)
+DL_Group::DL_Group(PrimeType type, u32bit pbits, u32bit qbits)
    {
    if(pbits < 512)
       throw Invalid_Argument("DL_Group: prime size " + to_string(pbits) +
@@ -51,7 +51,9 @@ DL_Group::DL_Group(u32bit pbits, PrimeType type)
       {
       if(type == Prime_Subgroup)
          {
-         const u32bit qbits = 2 * dl_work_factor(pbits);
+         if(!qbits)
+            qbits = 2 * dl_work_factor(pbits);
+
          q = random_prime(qbits);
          BigInt X;
          while(p.bits() != pbits || !is_prime(p))
@@ -61,7 +63,10 @@ DL_Group::DL_Group(u32bit pbits, PrimeType type)
             }
          }
       else
-         generate_dsa_primes(p, q, pbits);
+         {
+         qbits = qbits ? qbits : ((pbits == 1024) ? 160 : 256);
+         generate_dsa_primes(p, q, pbits, qbits);
+         }
 
       g = make_dsa_generator(p, q);
       }
@@ -72,9 +77,9 @@ DL_Group::DL_Group(u32bit pbits, PrimeType type)
 /*************************************************
 * DL_Group Constructor                           *
 *************************************************/
-DL_Group::DL_Group(const MemoryRegion<byte>& seed, u32bit pbits, u32bit start)
+DL_Group::DL_Group(const MemoryRegion<byte>& seed, u32bit pbits, u32bit qbits)
    {
-   if(!generate_dsa_primes(p, q, seed.begin(), seed.size(), pbits, start))
+   if(!generate_dsa_primes(p, q, pbits, qbits, seed))
       throw Invalid_Argument("DL_Group: The seed/counter given does not "
                              "generate a DSA group");