The design for the Chinook originates from the Vertol Model 107, which was produced by Boeing Vertol in the early 1960s. The Vertol was one of the pioneer twin rotor cargo helicopters developed by Boeing. Chinooks are now used in both military and civilian roles by more than 16 nations.
SHA-1 HMAC Generation. In cryptography, a keyed-hash message authentication code (HMAC) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key. It may be used to simultaneously verify both the data integrity and the authentication of a message, as with any MAC.
For HMAC-MD5 the RFC summarizes that-although the security of the MD5 hash function itself is severely compromised-the currently known  attacks on HMAC-MD5 do not seem to indicate a practical vulnerability when used as a message authentication code..he following is a Python implementation of HMAC-MD5: Python includes an hmac module, so the function above can be replaced by a shorter version. The following is a PHP implementation of HMAC-SHA1: PHP includes an hmac function, so the example above can be replaced by a shorter version.