$1.$ The very first step in the SHA$1$ algorithm is to pad the messageso that it is a multiple of $512$ bits. This padding occurs as follows $($from NIST FPS $180-2)$: Suppose the length of the message M is L bits. Append bit $1$ to the end of the message, followed by K zero bits where K is the smallest non$-$negative solution to L $+1+$ K $448($mod $512)$ Next append a $64-$bit block thatis a binary representation ofthe length integer L$.$ For example, Message $=$ "abc" length L $=24$ bits $011000010110001001100011100.....\mathrm{.}00000..\mathrm{.}011000$ a b c $<---423---><---64--------><512>$ Now here is the question: Why do we include the length of themessage in the calculation of the hash code?