frobbed executable puzzle

games/compaq/memfrob/Makefile

@@ -0,0 +1,9 @@
+LDFLAGS = -static
+
+all: frob main
+
+main: CFLAGS = -Dfrobbed='"$(shell tr -d '\n' < key | ./frob)"'
+
+clean:
+	rm -rf main frob
+

games/compaq/memfrob/frob.c

@@ -0,0 +1,13 @@
+#include <unistd.h>
+
+int
+main(int argc, char *argv[])
+{
+  char c;
+
+  while (read(0, &c, 1)) {
+    c ^= 3;
+    write(1, &c, 1);
+  }
+  return 0;
+}

games/compaq/memfrob/key

@@ -0,0 +1 @@
+lawful forths Amanda

games/compaq/memfrob/main.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <string.h>
+
+int
+main(int argc, char *argv[])
+{
+  char reply[256];
+
+  printf("What is the password? ");
+  fflush(stdout);
+  if (fgets(reply, sizeof(reply), stdin)) {
+    char *p;
+
+    for (p = reply; *p; p += 1) {
+      if ('\n' == *p) {
+        *p = '\0';
+        break;
+      }
+      *p = *p ^ 3;
+    }
+    if (strcmp(reply, frobbed)) {
+      printf("No it isn't!\n");
+    } else {
+      printf("Congratulations.\n");
+    }
+  }
+
+  return 0;
+}