core.BlockInitializer{,Test}: remove RNGs

LFSR PRNGs cannot be properly implemented

src/main/scala/uk/ac/soton/ecs/can/core/BlockInitializer.scala

 package uk.ac.soton.ecs.can.core
 
 import chisel3._
-import chisel3.util.random.GaloisLFSR
 
 class BlockInitializer extends MultiIOModule {
   val fillConstants = IO(Input(Bool()))
-  val generateKey = IO(Input(Bool()))
   val incrementBlockCount = IO(Input(Bool()))
-  val generateNonce = IO(Input(Bool()))
   val in = IO(Input(Vec(16, UInt(32.W))))
   val out = IO(Output(Vec(16, UInt(32.W))))
 
@@ -17,9 +14,7 @@ class BlockInitializer extends MultiIOModule {
     "h79622d32".U(32.W),
     "h6b206574".U(32.W)
   )
-  private val randomKey = (0 until 16).map(_ => GaloisLFSR.maxPeriod(32))
   private val incrementedBlockCount = in(12) + 1.U(32.W)
-  private val randomNonce = (0 until 3).map(_ => GaloisLFSR.maxPeriod(32))
 
   private val io = in.zip(out)
 
@@ -27,15 +22,11 @@ class BlockInitializer extends MultiIOModule {
     o := Mux(fillConstants, c, i)
   }
 
-  io.slice(4, 12).zip(randomKey).foreach { case ((i, o), k) =>
-    o := Mux(generateKey, k, i)
-  }
+  io.slice(4, 12).foreach { case (i, o) => o := i }
 
   io(12) match {
     case (i, o) => o := Mux(incrementBlockCount, incrementedBlockCount, i)
   }
 
-  io.takeRight(3).zip(randomNonce).foreach { case ((i, o), n) =>
-    o := Mux(generateNonce, n, i)
-  }
+  io.takeRight(3).foreach { case (i, o) => o := i }
 }

src/test/scala/uk/ac/soton/ecs/can/core/BlockInitializerTest.scala

@@ -25,23 +25,6 @@ class BlockInitializerTest extends FlatSpec with ChiselScalatestTester {
     }
   }
 
-  it should "randomly generate some keys when requested" in {
-    test(new BlockInitializer) { c =>
-      c.in.zip(input).foreach { case (p, n) => p.poke(n) }
-
-      c.generateKey.poke(true.B)
-      (0 until 10).foreach { _ =>
-        c.out.take(4).foreach(_.expect(0.U(32.W)))
-        c.out.slice(4, 12).foreach(o => assert(o.peek().litValue() != 0))
-        c.out.takeRight(4).foreach(_.expect(0.U(32.W)))
-        c.clock.step()
-      }
-
-      c.generateKey.poke(false.B)
-      c.out.foreach(_.expect(0.U(32.W)))
-    }
-  }
-
   it should "increment the block count when requested" in {
     test(new BlockInitializer) { c =>
       c.in.zip(input).foreach { case (p, n) => p.poke(n) }
@@ -59,20 +42,4 @@ class BlockInitializerTest extends FlatSpec with ChiselScalatestTester {
     }
   }
 
-  it should "randomly generate some nonce when requested" in {
-    test(new BlockInitializer) { c =>
-      c.in.zip(input).foreach { case (p, n) => p.poke(n) }
-
-      c.generateNonce.poke(true.B)
-      (0 until 10).foreach { _ =>
-        c.out.take(9).foreach(_.expect(0.U(32.W)))
-        c.out.takeRight(3).foreach(o => assert(o.peek().litValue() != 0))
-        c.clock.step()
-      }
-
-      c.generateNonce.poke(false.B)
-      c.out.foreach(_.expect(0.U(32.W)))
-    }
-  }
-
 }