# Why does Merkle-Damgård hashing involve putting the padding at the end instead of at the start?

Pretty much the title. We have that $$x$$ is a prefix of $$PAD(x)$$, instead of being a suffix - was that an arbitrary choice or is there a reason for it? Thank you.

• @kelalaka I appreciate that as a general rule, padding should be suffix-free, but I am not too sure why putting the message at the end rather than the start would exacerbate the potential suffix problem? Thank you. Apr 29 at 14:08
• @kelalaka That makes sense, thank you! Apr 29 at 14:39
• OK. I've converted the comment into an asnwer. Apr 29 at 15:17