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  • Bradley Ross thinks this is interesting:

Most hash algorithms use block mode to process; that is, they process all input in set blocks of data such as 512-bit blocks. The final hash is typically generated by adding the output blocks together to form the final output string of 160 or 512 bits.


Cover of Principles of Computer Security: CompTIA Security+ and Beyond, Fifth Edition, 5th Edition


Is adding the values truly appropriate. If the hash for each block is random, the sum of all of the will be close to the midpoint of the range. Perhaps this was meant to append the bits for each block into a series of 160 or 512 bits values. The values could be added or X-Ored to provide a more random value.