diff --git a/PaymentServer.cabal b/PaymentServer.cabal
index dd51a39404009e27bf993c5eac9c2842374ef8e2..c5a6aef4f0dd0588a9a88a9e0cb3d6e93a2c32e3 100644
--- a/PaymentServer.cabal
+++ b/PaymentServer.cabal
@@ -44,7 +44,7 @@ library
                      , sqlite-simple
   default-language:    Haskell2010
   ghc-options:       -Wmissing-import-lists -Wunused-imports
-  pkgconfig-depends: ristretto
+  pkgconfig-depends: libchallenge_bypass_ristretto
 
 executable PaymentServer-exe
   hs-source-dirs:      app
diff --git a/nix/PaymentServer.nix b/nix/PaymentServer.nix
index 0816f96d9959f118ef572b0673ad83abbfd210e1..98421eb30f09b35a5cccff8f4e8e1ccee3f7d050 100644
--- a/nix/PaymentServer.nix
+++ b/nix/PaymentServer.nix
@@ -2,19 +2,19 @@ let
   buildDepError = pkg:
     builtins.throw ''
       The Haskell package set does not contain the package: ${pkg} (build dependency).
-      
+
       If you are using Stackage, make sure that you are using a snapshot that contains the package. Otherwise you may need to update the Hackage snapshot you are using, usually by updating haskell.nix.
       '';
   sysDepError = pkg:
     builtins.throw ''
       The Nixpkgs package set does not contain the package: ${pkg} (system dependency).
-      
+
       You may need to augment the system package mapping in haskell.nix so that it can be found.
       '';
   pkgConfDepError = pkg:
     builtins.throw ''
       The pkg-conf packages does not contain the package: ${pkg} (pkg-conf dependency).
-      
+
       You may need to augment the pkg-conf package mapping in haskell.nix so that it can be found.
       '';
   exeDepError = pkg:
@@ -24,16 +24,16 @@ let
   legacyExeDepError = pkg:
     builtins.throw ''
       The Haskell package set does not contain the package: ${pkg} (executable dependency).
-      
+
       If you are using Stackage, make sure that you are using a snapshot that contains the package. Otherwise you may need to update the Hackage snapshot you are using, usually by updating haskell.nix.
       '';
   buildToolDepError = pkg:
     builtins.throw ''
       Neither the Haskell package set or the Nixpkgs package set contain the package: ${pkg} (build tool dependency).
-      
+
       If this is a system dependency:
       You may need to augment the system package mapping in haskell.nix so that it can be found.
-      
+
       If this is a Haskell dependency:
       If you are using Stackage, make sure that you are using a snapshot that contains the package. Otherwise you may need to update the Hackage snapshot you are using, usually by updating haskell.nix.
       '';
@@ -78,7 +78,7 @@ in { system, compiler, flags, pkgs, hsPkgs, pkgconfPkgs, ... }:
           (hsPkgs."sqlite-simple" or (buildDepError "sqlite-simple"))
           ];
         pkgconfig = [
-          (pkgconfPkgs."ristretto" or (pkgConfDepError "ristretto"))
+          (pkgconfPkgs."libchallenge_bypass_ristretto" or (pkgConfDepError "libchallenge_bypass_ristretto"))
           ];
         };
       exes = {
@@ -97,4 +97,4 @@ in { system, compiler, flags, pkgs, hsPkgs, pkgconfPkgs, ... }:
           };
         };
       };
-    } // rec { src = (pkgs.lib).mkDefault ../.; }
\ No newline at end of file
+    } // rec { src = (pkgs.lib).mkDefault ../.; }
diff --git a/nix/challenge-bypass-ristretto-repo.nix b/nix/challenge-bypass-ristretto-repo.nix
new file mode 100644
index 0000000000000000000000000000000000000000..c7e246f6c2bfb2b8b2fb73bc02ef38b818ac4ddf
--- /dev/null
+++ b/nix/challenge-bypass-ristretto-repo.nix
@@ -0,0 +1,9 @@
+let
+  pkgs = import <nixpkgs> {};
+in
+  pkgs.fetchFromGitHub {
+    owner = "LeastAuthority";
+    repo = "python-challenge-bypass-ristretto";
+    rev = "f1a7cfab1a7f1bf8b3345c228c2183064889ad83";
+    sha256 = "12myak2jwaisljs7bmx1vydgd0fnxvkaisk4zsf0kshwxrlnyh3x";
+  }
\ No newline at end of file
diff --git a/nix/challenge-bypass-ristretto.nix b/nix/challenge-bypass-ristretto.nix
new file mode 100644
index 0000000000000000000000000000000000000000..cded558877b038c7e8c87a82e328f0a8650a3516
--- /dev/null
+++ b/nix/challenge-bypass-ristretto.nix
@@ -0,0 +1,5 @@
+{ fetchFromGitHub, callPackage }:
+let
+  src = import ./challenge-bypass-ristretto-repo.nix;
+in
+  callPackage "${src}/challenge-bypass-ristretto.nix" { }
diff --git a/nix/overlay.nix b/nix/overlay.nix
index 2673b39a9a30912c088deed29eeaa6a698e0f232..482cbb066d6bb562c8046d9e73285aff2c38d199 100644
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@@ -1,3 +1,3 @@
 self: super: {
-  ristretto = super.callPackage ./ristretto.nix { };
+  challenge-bypass-ristretto = super.callPackage ./challenge-bypass-ristretto.nix { };
 }
diff --git a/nix/privacypass-repo.nix b/nix/privacypass-repo.nix
deleted file mode 100644
index 6b0c64cff07889c23400e15e1d2824d3ac8905cf..0000000000000000000000000000000000000000
--- a/nix/privacypass-repo.nix
+++ /dev/null
@@ -1,7 +0,0 @@
-{ fetchFromGitHub }:
-fetchFromGitHub {
-  owner = "LeastAuthority";
-  repo = "privacypass";
-  rev = "45855401e163f8e622bd93a5c5bce13de8c8510a";
-  sha256 = "sha256:15wv8vas6x8cdicylp0m632c916p7qxq1k4lnchr8c92lldp0rv7";
-}
diff --git a/nix/ristretto.nix b/nix/ristretto.nix
deleted file mode 100644
index 4e0912840d99a23263408dd86be620e23c92d7e3..0000000000000000000000000000000000000000
--- a/nix/ristretto.nix
+++ /dev/null
@@ -1,5 +0,0 @@
-{ fetchFromGitHub, callPackage }:
-let
-  src = import ./privacypass-repo.nix { inherit fetchFromGitHub; };
-in
-  callPackage "${src}/ristretto.nix" { }
diff --git a/ristretto.nix b/ristretto.nix
deleted file mode 100644
index 8af584c022d28a62c6b3ec5c1dd9638e8c4a6325..0000000000000000000000000000000000000000
--- a/ristretto.nix
+++ /dev/null
@@ -1,10 +0,0 @@
-{ fetchFromGitHub, callPackage }:
-let
-  src = fetchFromGitHub {
-    owner = "LeastAuthority";
-    repo = "privacypass";
-    rev = "45855401e163f8e622bd93a5c5bce13de8c8510a";
-    sha256 = "15wv8vas6x8cdicylp0m632c916p7qxq1k4lnchr8c92lldp0rv7";
-  };
-in
-  callPackage "${src}/ristretto.nix" { }
diff --git a/shell.nix b/shell.nix
index b474e0029a87c9da6fcdec474f80089c1aa05a2c..5b5500af771778732fef0ffbe0f0104c38fe8d3e 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,6 +1,16 @@
 { pkgs ? import <nixpkgs> { } }:
-pkgs.mkShell {
-  buildInputs = [
-    pkgs.stack
-  ];
-}
+let
+  haskellDotNix = pkgs.fetchFromGitHub {
+    owner = "input-output-hk";
+    repo = "haskell.nix";
+    rev = "33dc7bce3444f8957dec9dccb484dd4b40ee463d";
+    sha256 = "0ffv3sfjkba4b565gpgs0qznd2jh5v60ql03dkc5bgx2sh8yfhsv";
+  };
+  nix-tools = (import pkgs.path (import haskellDotNix)).haskell-nix.nix-tools;
+in
+  pkgs.mkShell {
+    buildInputs = [
+      pkgs.stack
+      nix-tools
+    ];
+  }
diff --git a/stack-shell.nix b/stack-shell.nix
index 8800cbbd773f7386033d30036ff026a169420e5f..bcbca4e2d6c8184374da5db1be50fb9ae2fd1a42 100644
--- a/stack-shell.nix
+++ b/stack-shell.nix
@@ -3,15 +3,15 @@
 { ghc }:
 let
   pkgs = import <nixpkgs> { };
-  # Get our Ristretto bindings.
-  ristretto = pkgs.callPackage ./ristretto.nix { };
+  # Get our bindings.
+  challenge-bypass-ristretto = pkgs.callPackage ./nix/challenge-bypass-ristretto.nix { };
 in
   # This is what you're supposed to call in a stack shell-file.  I don't
   # *really* know what it does but I know it works...
   pkgs.haskell.lib.buildStackProject {
     inherit ghc;
-    name = "PrivacyPass";
+    name = "challenge-bypass-ristretto";
     # zlib is a common dependency of many of our dependencies.  and we put our
-    # ristretto library in as well.
-    buildInputs = [ pkgs.zlib ristretto ];
+    # challenge-bypass-ristretto library in as well.
+    buildInputs = [ pkgs.zlib challenge-bypass-ristretto ];
   }