Add wikipedia extlinks target. Warn about SRP verifier being secret

1 files changed, 16 insertions, 2 deletions

diff --git a/doc/srp.rst b/doc/srp.rst
index 03792c97e..e3aace5ff 100644
--- a/doc/srp.rst
+++ b/doc/srp.rst
@@ -1,8 +1,22 @@
 Secure Remote Password
 ========================================
 
-The library contains an implementation of the SRP-6a password based
-key exchange protocol in ``srp6.h``.
+The library contains an implementation of the :wikipedia:`SRP-6a
+password based key exchange protocol
+<Secure_remote_password_protocol>` in ``srp6.h``.
+
+A SRP client provides what is called a SRP *verifier* to the server.
+This verifier is based on a password, but the password cannot be
+easily derived from the verifier. Later, the client and server can
+perform an SRP exchange, in which
+
+ .. warning::
+
+     While knowledge of the verifier does not easily allow an attacker
+     to get the raw password, they could still use the verifier to
+     impersonate the server to the client, so verifiers should be
+     carefully protected.
+
 
 .. cpp:function:: BigInt generate_srp6_verifier( \
           const std::string& identifier, \