digest

From digest v0.1.0 by Dirk Eddelbuettel

Create hash function digests for arbitrary R objects

The digest function applies a cryptographical hash function to arbitrary R objects. By default, the objects are internally serialized, and either one of the currently implemented MD5 and SHA-1 hash functions algorithms can be used to compute a compact digest of the serialized object.

In order to compare this implementation with others, serialization of the input argument can also be turned off in which the input argument must be a character string for which its digest is returned.

Keywords: misc

Usage

digest(object, algo="md5", serialize=TRUE)

Arguments

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, and sha-1
serialize: A logical variable indicating whether the object should be serialized using serialize. Setting this to FALSE allows to compares the digest output of given character strings to known control output.

Details

Cryptographic hash functions are well researched and documented. The MD5 algorithm by Ron Rivest is specified in RFC 1321. The SHA-1 algorithm is specified in FIPS-180-1.

This R implementation relies on two standalone implementations in C by Christophe Devine.

Value

The digest function returns a character string of a fixed length containing the requested digest of the supplied R object. For MD5, a string of length 32 is returned; for SHA-1, a string of length 40 is returned.
NULL is returned if an bad argument for algo had been supplied.

References

MD5 is described in MD5 Message-Digest Algorithm at http://www.ietf.org/rfc/rfc1321.txt.

SHA-1 is described in Secure Hash Standard at http://www.itl.nist.gov/fipspubs/fip180-1.htm.

http://www.cr0.net:8040/code/crypto for the underlying C functions used here, and further references.

Examples

## Standard RFC 1321 test vectors
md5Input <-
  c("",
    "a",
    "abc",
    "message digest",
    "abcdefghijklmnopqrstuvwxyz",
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
    paste("12345678901234567890123456789012345678901234567890123456789012",
          "345678901234567890", sep=""))
md5Output <-
  c("d41d8cd98f00b204e9800998ecf8427e",
    "0cc175b9c0f1b6a831c399e269772661",
    "900150983cd24fb0d6963f7d28e17f72",
    "f96b697d7cb7938d525a2f31aaf161d0",
    "c3fcd3d76192e4007dfb496cca67e13b",
    "d174ab98d277d9f5a5611c2c9f419d9f",
    "57edf4a22be3c955ac49da2e2107b67a")

for (i in seq(along=md5Input)) {
  md5 <- digest(md5Input[i], serialize=FALSE)
  stopifnot(identical(md5, md5Output[i]))
}

sha1Input <-
  c("abc",
    "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
    NULL)
sha1Output <- 
  c("a9993e364706816aba3e25717850c26c9cd0d89d",
    "84983e441c3bd26ebaae4aa1f95129e5e54670f1",
    "34aa973cd4c4daa4f61eeb2bdbad27316534016f")

for (i in seq(along=sha1Input)) {
  sha1 <- digest(sha1Input[i], algo="sha1", serialize=FALSE)
  stopifnot(identical(sha1, sha1Output[i]))
}

# one of the FIPS-
sha1 <- digest("abc", algo="sha1", serialize=FALSE)
stopifnot(identical(sha1, "a9993e364706816aba3e25717850c26c9cd0d89d"))

# example of a digest of a standard R list structure
digest(list(LETTERS, data.frame(a=letters[1:5], b=matrix(1:10,ncol=2))))

Documentation reproduced from package digest, version 0.1.0, License: GPL Version 2

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