MD5 Hash Check (XMD5) - KB Article #2048Related Articles -- 2051, 2050, 2049, 1485
The XMD5 command asks the server to perform a cyclic redundancy check using the MD5 algorithm on the specified file. If the XMD5 command is supported, the server will respond with the result of the calculation. FTP clients can use this command to verify that the file was transferred without corruption by comparing the server's response with its own calculation.
MD5 was designed by Ron Rivest as a replacement to MD4. It operates by breaking the file into 512-bit blocks, and then padding the last block so that it is also 512 bits in length. The algorithm creates four 32-bit keywords which are then assigned as fixed constants. Each message block is then operated on in four rounds, each round consisting of 16 operations based on a non-linear function, producing the hash.