compute a hash-based message authentication code

The hmac function calculates a message authentication code (MAC) involving the specified cryptographic hash function in combination with a given secret key.

hmac(key, object,
     algo = c("md5", "sha1", "crc32", "sha256", "sha512"),
     serialize = FALSE, raw = FALSE, ...)

Arguments

key: An arbitrary character or numeric vector, to use as pre-shared secret key.
object: An arbitrary R object which will then be passed to the serialize function, unless the serialize argument is set to FALSE.
algo: The algorithms to be used; currently available choices are md5, which is also the default, sha1, crc32 and sha256.
serialize: default value of serialize is here FALSE, not TRUE as it is in digest.
raw: This flag alters the type of the output. Setting this to TRUE causes the function to return an object of type "raw" instead of "character".
...: All remaining arguments are passed to digest.

Value

The hmac function uses the digest to return a hash digest as specified in the RFC 2104.

References

MD5: https://www.ietf.org/rfc/rfc1321.txt.

SHA-1: https://en.wikipedia.org/wiki/SHA-1. SHA-256: https://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf. CRC32: The original reference webpage at rocksoft.com has vanished from the web; see https://en.wikipedia.org/wiki/Cyclic_redundancy_check for general information on CRC algorithms.

https://aarongifford.com/computers/sha.html for the integrated C implementation of sha-512.

The page for the code underlying the C functions used here for sha-1 and md5, and further references, is no longer accessible. Please see https://en.wikipedia.org/wiki/SHA-1 and https://en.wikipedia.org/wiki/MD5.

https://zlib.net for documentation on the zlib library which supplied the code for crc32.

https://en.wikipedia.org/wiki/SHA_hash_functions for documentation on the sha functions.

Author

Mario Frasca mfrasca@zonnet.nl.

Examples




## Standard RFC 2104 test vectors
current <- hmac('Jefe', 'what do ya want for nothing?', "md5")
target <- '750c783e6ab0b503eaa86e310a5db738'
stopifnot(identical(target, as.character(current)))

current <- hmac(rep(0x0b, 16), 'Hi There', "md5")
target <- '9294727a3638bb1c13f48ef8158bfc9d'
stopifnot(identical(target, as.character(current)))

current <- hmac(rep(0xaa, 16), rep(0xdd, 50), "md5")
target <- '56be34521d144c88dbb8c733f0e8b3f6'
stopifnot(identical(target, as.character(current)))

## SHA1 tests inspired to the RFC 2104 and checked against the python
## hmac implementation.
current <- hmac('Jefe', 'what do ya want for nothing?', "sha1")
target <- 'effcdf6ae5eb2fa2d27416d5f184df9c259a7c79'
stopifnot(identical(target, as.character(current)))

current <- hmac(rep(0x0b, 16), 'Hi There', "sha1")
target <- '675b0b3a1b4ddf4e124872da6c2f632bfed957e9'
stopifnot(identical(target, as.character(current)))

current <- hmac(rep(0xaa, 16), rep(0xdd, 50), "sha1")
target <- 'd730594d167e35d5956fd8003d0db3d3f46dc7bb'
stopifnot(identical(target, as.character(current)))