move group14 and group16 to options.h, group14-sha256 on by default
diff --git a/options.h b/options.h
index 0c51bb1..89b68be 100644
--- a/options.h
+++ b/options.h
@@ -168,10 +168,20 @@
* ECDSA above */
#define DROPBEAR_ECDH
-/* Group14 (2048 bit) is recommended. Group1 is less secure (1024 bit) though
- is the only option for interoperability with some older SSH programs */
+/* Key exchange algorithm.
+ * group1 - 1024 bit, sha1
+ * group14 - 2048 bit, sha1
+ * group14_256 - 2048 bit, sha2-256
+ * group16 - 4096 bit, sha2-512
+ *
+ * group14 is supported by most implementations.
+ * group16 provides a greater strength but is slower and increases binary size
+ * group1 is necessary if compatibility with Dropbear versions < 0.53 is required
+ */
#define DROPBEAR_DH_GROUP1 1
#define DROPBEAR_DH_GROUP14 1
+#define DROPBEAR_DH_GROUP14_256 1
+#define DROPBEAR_DH_GROUP16 0
/* Control the memory/performance/compression tradeoff for zlib.
* Set windowBits=8 for least memory usage, see your system's
diff --git a/sysoptions.h b/sysoptions.h
index 9a76655..6bebce9 100644
--- a/sysoptions.h
+++ b/sysoptions.h
@@ -127,11 +127,6 @@
#define DROPBEAR_MD5
#endif
-/* These are disabled in Dropbear 2016.73 by default since the spec
- draft-ietf-curdle-ssh-kex-sha2-02 is under development. */
-#define DROPBEAR_DH_GROUP14_256 0
-#define DROPBEAR_DH_GROUP16 0
-
/* roughly 2x 521 bits */
#define MAX_ECC_SIZE 140
