Revert "xrcp: use SHA3-256 in hybrid key agreement (#1302)"

This reverts commit 67d3809.

protocol/xrcp.md

@@ -250,7 +250,7 @@ In pseudo-code:
 ```
 // session 1
 hostHelloSecret(1) = dhSecret(1)
-sessionSecret(1) = sha3-256(dhSecret(1) || kemSecret(1)) // to encrypt session 1 data, incl. controller hello
+sessionSecret(1) = sha256(dhSecret(1) || kemSecret(1)) // to encrypt session 1 data, incl. controller hello
 dhSecret(1) = dh(hostHelloDhKey(1), controllerInvitationDhKey(1))
 kemCiphertext(1) = enc(kemSecret(1), kemEncKey(1))
 // kemEncKey is included in host HELLO, kemCiphertext - in controller HELLO
@@ -262,7 +262,7 @@ dhSecret(n') = dh(hostHelloDhKey(n - 1), controllerDhKey(n))
 
 // session n
 hostHelloSecret(n) = dhSecret(n)
-sessionSecret(n) = sha3-256(dhSecret(n) || kemSecret(n)) // to encrypt session n data, incl. controller hello
+sessionSecret(n) = sha256(dhSecret(n) || kemSecret(n)) // to encrypt session n data, incl. controller hello
 dhSecret(n) = dh(hostHelloDhKey(n), controllerDhKey(n))
 // controllerDhKey(n) is either from invitation or from multicast announcement
 kemCiphertext(n) = enc(kemSecret(n), kemEncKey(n))

src/Simplex/Messaging/Crypto/SNTRUP761.hs

@@ -4,7 +4,7 @@
 
 module Simplex.Messaging.Crypto.SNTRUP761 where
 
-import Crypto.Hash (Digest, SHA3_256, hash)
+import Crypto.Hash (Digest, SHA256, hash)
 import Data.ByteArray (ScrubbedBytes)
 import qualified Data.ByteArray as BA
 import Data.ByteString (ByteString)
@@ -28,4 +28,4 @@ kcbEncrypt (KEMHybridSecret k) = sbEncrypt_ k
 kemHybridSecret :: PublicKeyX25519 -> PrivateKeyX25519 -> KEMSharedKey -> KEMHybridSecret
 kemHybridSecret k pk (KEMSharedKey kem) =
   let DhSecretX25519 dh = C.dh' k pk
-   in KEMHybridSecret $ BA.convert (hash $ BA.convert dh <> kem :: Digest SHA3_256)
+   in KEMHybridSecret $ BA.convert (hash $ BA.convert dh <> kem :: Digest SHA256)