Question

how i solve this quistion ?

Based on MD5 hash algorithm, M₁ required 10 blocks and padding size is 8 bits. M₂ required 3 blocks and padding size is 480 bits. If M₁ and M₂ are combined in a single file called M₃. Find M₃ size

Answer 1

Solution for the problem is provided below. Please comment if you have any doubt.

It is given that there are two messages, M1 and M2.

M1- required 10 blocks and the padding size is 8 bits

M2-require 3 blocks and the padding size is 460

It is known that MD5 hash algorithm process the input message in blocks of 512 bits and if 512 bits are not available for a block, the remaining blocks will be filled by padded bits.

Here M1 requires 10 blocks that is it will have, 10*512 = 5120 bits including the 8 bits pad.

Number of actual bits of M1= 5120-8 = 5112 bits

Here M2 requires 3 blocks that is it will have, 3*512 = 1536 bits including the 480 bits pad.

Number of actual bits of M2= 1536-480 = 1056 bits

M3 is made by combining M1 and M2, then the size of M3 = 5112+1056 = 6168 bits

The size of M3 = 6168 bits = 771 bytes