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This is especially true of cryptographic hash functions, which may be used to detect many data corruption errors and verify overall data integrity; if the computed checksum for the current data input matches the stored value of a previously computed checksum, there is a very high probability the data has not been accidentally altered or corrupted.
It worked by breaking up the data to be sent into 128-byte packets, adding a 3-byte header and 1-byte checksum footer, and sending the resulting 132-byte packets out in order. The receiving computer recalculated the checksum from the 128 bytes of data, and if it matched the checksum sent in the footer it sent back an ACK , and if it did not ...
The Fletcher checksum cannot distinguish between blocks of all 0 bits and blocks of all 1 bits. For example, if a 16-bit block in the data word changes from 0x0000 to 0xFFFF, the Fletcher-32 checksum remains the same. This also means a sequence of all 00 bytes has the same checksum as a sequence (of the same size) of all FF bytes.
Paul Hsieh's SuperFastHash [1] 32 bits Buzhash: variable XOR/table Fowler–Noll–Vo hash function (FNV Hash) 32, 64, 128, 256, 512, or 1024 bits xor/product or product/XOR Jenkins hash function: 32 or 64 bits XOR/addition Bernstein's hash djb2 [2] 32 or 64 bits shift/add or mult/add or shift/add/xor or mult/xor PJW hash / Elf Hash: 32 or 64 bits
The Internet checksum, [1] [2] also called the IPv4 header checksum is a checksum used in version 4 of the Internet Protocol (IPv4) to detect corruption in the header of IPv4 packets. It is carried in the IPv4 packet header , and represents the 16-bit result of the summation of the header words.
10 0001 0000 1: byte → value push a byte onto the stack as an integer value: breakpoint ca 1100 1010 reserved for breakpoints in Java debuggers; should not appear in any class file caload 34 0011 0100 arrayref, index → value load a char from an array castore 55 0101 0101 arrayref, index, value → store a char into an array checkcast c0 ...
For example, the SCSI and PCI buses use parity to detect transmission errors, and many microprocessor instruction caches include parity protection. Because the Instruction cache data is just a copy of the main memory , it can be disregarded and refetched if it is found to be corrupted.
This is actually a single permutation (1 5 8 9 4 2 7 0)(3 6) applied iteratively; i.e. p(i+j,n) = p(i, p(j,n)). The Verhoeff checksum calculation is performed as follows: Create an array n out of the individual digits of the number, taken from right to left (rightmost digit is n 0, etc.). Initialize the checksum c to zero.