The algorithm takes as input a message with a maximum

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the previous iteratin, and the output from W. The algorithm takes as input a message with a maximum length of less than 2 256 bits and produces as output a 512-bit message digest. The input is processed in 512-bit blocks. Figure 1 depicts the overall processing of a message to produce a digest. The processing consists of the following steps: Step 1: Append padding bits: The message is padded so that its length in bits is an odd multiple of 256. Padding is always added, even if the message is already of the desired length. For example, if the message is 256 x 3 = 768 bits long, it is padded by 512 bits to a length of 256 x 5=1,280 bits. Thus, the number of padding bits is in the range of 1 to 512.The padding consists of a single 1-bit followed by the necessary number of 0-bits. Step 2: Append length . A block of 256 bits is appended to the message. This block is treated as an unsigned 256-bit integer (most significant byte first) and contains the length in bits of the original message (before the padding). The outcome of the first two steps yields a message that is an integer multiple of 512 bits in length. In Figure 1, the expanded message is represented as the sequence of 512-bit blocks m 1 , m 2 , ….,m t , so that the total length of the expanded message is tx512 bits. These blocks are viewed externally as arrays of bytes by sequentially grouping the bits in 8-bit chunks. However, internally, the hash state Hi is viewed as an 8 x 8 matrix of bytes. The transformation between the two is explained subsequently. Step 3: Initialize hash matrix : An 8x8 matrix of bytes is used to hold intermediate and final results of the hash function. The matrix is initialized as consisting of all 0- bits.
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  • Fall '18
  • hash function, Whirlpool, Cryptographic hash function

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