From ffa4c9eac06b8046ae159a5a2ef96ca86b53227e Mon Sep 17 00:00:00 2001
From: Sebastian Nagel <sebastian.nagel@ncoding.at>
Date: Tue, 11 Jul 2023 17:50:12 +0200
Subject: [PATCH 1/2] Fix compilation of CryptoSpec

---
 hydra-node/test/Hydra/CryptoSpec.hs | 37 ++++++++++++++---------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/hydra-node/test/Hydra/CryptoSpec.hs b/hydra-node/test/Hydra/CryptoSpec.hs
index cfc2c7f88d8..aa479b9da7f 100644
--- a/hydra-node/test/Hydra/CryptoSpec.hs
+++ b/hydra-node/test/Hydra/CryptoSpec.hs
@@ -13,18 +13,20 @@ import Cardano.Crypto.PinnedSizedBytes (psbFromByteString)
 import qualified Data.ByteString as BS
 import qualified Data.ByteString.Char8 as Char8
 import qualified Data.Map as Map
+import Hydra.Party (Party (vkey), deriveParty)
 import Test.Aeson.GenericSpecs (roundtripAndGoldenSpecs)
 import Test.QuickCheck (
-  conjoin,
   counterexample,
+  elements,
   forAll,
   shuffle,
+  sublistOf,
   (=/=),
-  (==>), chooseInt,
+  (===),
+  (==>),
  )
 import Test.QuickCheck.Instances.UnorderedContainers ()
 import Test.Util (propCollisionResistant)
-import Data.List ((!!))
 
 spec :: Spec
 spec = do
@@ -92,24 +94,21 @@ specMultiSignature =
             not (null shuffled)
               ==> verifyMultiSignature (map vkey shuffled) (aggregateInOrder sigs shuffled) msg
               === Verified
-       in verifyMultiSignature vks msig msg
 
     prop "verifyMultiSignature fails when signature is missing" $ \sks (msg :: ByteString) dummySig ->
-      (length sks > 2) ==>
-        forAll (elements sks) $ \missingKeySig ->
-              sigs = (\sk -> if sk /= missingKeySig then sign sk msg else dummySig) <$> sks
-           in not (verifyMultiSignature (map getVerificationKey sks) (aggregate sigs) msg)
+      (length sks > 2)
+        ==> forAll (elements sks)
+        $ \missingKeySig ->
+          let sigs = (\sk -> if sk /= missingKeySig then sign sk msg else dummySig) <$> sks
+           in verifyMultiSignature (map getVerificationKey sks) (aggregate sigs) msg
+                =/= Verified
 
     prop "does not validate multisig if less keys given" $ \sks (msg :: ByteString) -> do
       (length sks > 1)
-      properPrefixes <- sublistOf sks
-        ==> let sigs = aggregate $ map (`sign` msg) (toList sks)
-            conjoin
-                  ( map
-                      ( \prefix ->
-                          not (verifyMultiSignature (map getVerificationKey prefix) sigs msg)
-                            & counterexample ("Prefix: " <> show prefix)
-                            & counterexample ("Signature: " <> show sigs)
-                      )
-                      properPrefixes
-                  )
+        ==> forAll (sublistOf sks)
+        $ \prefix ->
+          let sigs = aggregate $ map (`sign` msg) (toList sks)
+           in verifyMultiSignature (map getVerificationKey prefix) sigs msg
+                =/= Verified
+                & counterexample ("Keys: " <> show prefix)
+                & counterexample ("Signature: " <> show sigs)

From fbaa3eb44ee01a305c2a7fc1d761249222533066 Mon Sep 17 00:00:00 2001
From: Sebastian Nagel <sebastian.nagel@ncoding.at>
Date: Tue, 11 Jul 2023 17:54:30 +0200
Subject: [PATCH 2/2] Test strictly smaller sub lists and classify results

sublistOf is also sometimes yielding the same list, so we discard same
length prefixes. Also, classifying empty lists helps in ensuring we have
actually non trivial cases.
---
 hydra-node/test/Hydra/CryptoSpec.hs | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/hydra-node/test/Hydra/CryptoSpec.hs b/hydra-node/test/Hydra/CryptoSpec.hs
index aa479b9da7f..a0169ff56b0 100644
--- a/hydra-node/test/Hydra/CryptoSpec.hs
+++ b/hydra-node/test/Hydra/CryptoSpec.hs
@@ -16,6 +16,7 @@ import qualified Data.Map as Map
 import Hydra.Party (Party (vkey), deriveParty)
 import Test.Aeson.GenericSpecs (roundtripAndGoldenSpecs)
 import Test.QuickCheck (
+  classify,
   counterexample,
   elements,
   forAll,
@@ -104,11 +105,11 @@ specMultiSignature =
                 =/= Verified
 
     prop "does not validate multisig if less keys given" $ \sks (msg :: ByteString) -> do
-      (length sks > 1)
-        ==> forAll (sublistOf sks)
-        $ \prefix ->
-          let sigs = aggregate $ map (`sign` msg) (toList sks)
-           in verifyMultiSignature (map getVerificationKey prefix) sigs msg
-                =/= Verified
-                & counterexample ("Keys: " <> show prefix)
-                & counterexample ("Signature: " <> show sigs)
+      forAll (sublistOf sks) $ \prefix ->
+        (length prefix < length sks)
+          ==> let sigs = aggregate $ map (`sign` msg) (toList sks)
+               in verifyMultiSignature (map getVerificationKey prefix) sigs msg
+                    =/= Verified
+                    & classify (null prefix) "empty"
+                    & counterexample ("Keys: " <> show prefix)
+                    & counterexample ("Signature: " <> show sigs)