Add Ed25519 tests and secret key conversion

ccryptolib/ed25519.lua

@@ -11,6 +11,11 @@ local random = require "ccryptolib.random"
 
 local mod = {}
 
+--- Converts a signing key to an equivalent exchange key.
+function mod.exchangeKey(sk)
+    return sha512.digest(sk):sub(1, 32)
+end
+
 --- Computes a public key from a secret key.
 --
 -- @tparam string sk A random 32-byte secret key.

spec/ed25519_spec.lua

@@ -8,6 +8,10 @@ local ed25519 = require "ccryptolib.ed25519"
 
 describe("ed25519.verify", function()
     it("passes the section 7.1 test 1", function()
+        local sk = util.hexcat {
+            "9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60",
+        }
+
         local pk = util.hexcat {
             "d75a980182b10ab7d54bfed3c964073a0ee172f3daa62325af021a68f707511a",
         }
@@ -19,10 +23,15 @@ describe("ed25519.verify", function()
             "5fb8821590a33bacc61e39701cf9b46bd25bf5f0595bbe24655141438e7a100b",
         }
 
+        expect(ed25519.publicKey(sk)):eq(pk)
         expect(ed25519.verify(pk, m, sig)):eq(true)
     end)
 
     it("passes the section 7.1 test 2", function()
+        local sk = util.hexcat {
+            "4ccd089b28ff96da9db6c346ec114e0f5b8a319f35aba624da8cf6ed4fb8a6fb",
+        }
+
         local pk = util.hexcat {
             "3d4017c3e843895a92b70aa74d1b7ebc9c982ccf2ec4968cc0cd55f12af4660c",
         }
@@ -36,10 +45,15 @@ describe("ed25519.verify", function()
             "085ac1e43e15996e458f3613d0f11d8c387b2eaeb4302aeeb00d291612bb0c00",
         }
 
+        expect(ed25519.publicKey(sk)):eq(pk)
         expect(ed25519.verify(pk, m, sig)):eq(true)
     end)
 
     it("passes the section 7.1 test 3", function()
+        local sk = util.hexcat {
+            "c5aa8df43f9f837bedb7442f31dcb7b166d38535076f094b85ce3a2e0b4458f7",
+        }
+
         local pk = util.hexcat {
             "fc51cd8e6218a1a38da47ed00230f0580816ed13ba3303ac5deb911548908025",
         }
@@ -53,6 +67,7 @@ describe("ed25519.verify", function()
             "18ff9b538d16f290ae67f760984dc6594a7c15e9716ed28dc027beceea1ec40a",
         }
 
+        expect(ed25519.publicKey(sk)):eq(pk)
         expect(ed25519.verify(pk, m, sig)):eq(true)
     end)