suggestions

reverse-engineering/cimg-magic-number/DESCRIPTION.md

@@ -17,3 +17,17 @@ Of course, to you, this looks like a semantic-bearing string of characters, but
 In this challenge, you must craft a file with a `cimg` extension that contains the correct magic number.
 You can learn this magic number by reversing the `/challenge/cimg` binary.
 If you properly get past the magic number check, the challenge will give you the flag!
+
+----
+**Approach Suggestions:**
+Some hopefully-useful suggestions to get you started:
+
+- Reverse engineering can be done "statically" (e.g., in a graphical reversing tool such as IDA and the like, with the program you are trying to understand remaining "at rest") or "dynamically" (e.g., in a debugger such as gdb, with the program you are trying to understand running).
+  We recommend a combination of these techniques throughout this module.
+  Use your graphical reversing tool to form hypotheses about the program (e.g., "it compares some bytes of my input against something at this assembly instruction address") and then verify these hypotheses in gdb (e.g., break at the address in question, look at the values of the registers it compares, and correlate them with your input).
+- **Leave objdump behind.** You might have used objdump previously to look at assembly code.
+  You might be able to solve this level (and maybe the next) with objdump, but **you cannot do this module** without a good graphical reversing tool.
+  Use this challenge as impetus to begin gaining familiarity with a graphical reversing tool.
+- Retrace your successful solution.
+  If you solve this challenge without using _both_ a graphical reversing tool and a debugger (gdb), go back and re-verify your solution using the tools that you did not use.
+  This will be good practice for understanding how to use these tools in later levels, and you should apply it in any challenge that you solve without relying on both tools.