Computes the SHA-256 hash (FIPS 180-4) of text or raw bytes with the
self-contained implementation in the package's compiled core, and returns
it as a 64-character lowercase hexadecimal string. A hash is a short
fingerprint: any change to the input changes it, so it is used throughout
the package to record exactly which data, mapping or file a result came
from. Sibling packages use the same routine through
LinkingTo: rmoriebricklayer.
Arguments
- x
A character vector, or a raw vector. Other atomic vectors are converted with
as.character().
Value
A character vector of 64-character lowercase hex digests: one per
element for character input, length 1 for raw input
(character(0) for an empty character vector).
Details
For a raw vector the bytes are hashed as one message and one digest is
returned. Any other input is converted with as.character() and each
element is hashed separately, as the bytes of the string as stored in
memory (no re-encoding). In a UTF-8 session those are the UTF-8 bytes;
for a string marked latin1 they are the latin1 bytes, so use
enc2utf8() first when the digest must be the same on every
platform. NA gives NA. Numbers are hashed through their
printed form (1 hashes as "1"), and a factor through its
labels.
For a digest of a whole R object, hash its serialization (see the
examples) or use dgstobj; for BLAKE2b use
cblake2b.
References
National Institute of Standards and Technology (2015). Secure Hash Standard (SHS). FIPS PUB 180-4. doi:10.6028/NIST.FIPS.180-4
Examples
# Hash a character scalar (NIST test vector for "abc").
csha256("abc")
#> [1] "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
# ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad
# Vectorised over character input: one digest per element.
csha256(c("abc", "def", NA))
#> [1] "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
#> [2] "cb8379ac2098aa165029e3938a51da0bcecfc008fd6795f401178647f96c5b34"
#> [3] NA
# Raw input hashes the bytes directly; identical to the character form.
identical(csha256("abc"), csha256(charToRaw("abc")))
#> [1] TRUE
# The empty message.
csha256(raw(0))
#> [1] "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
# Fingerprint an arbitrary object via its serialization.
csha256(serialize(list(a = 1L, b = "x"), NULL))
#> [1] "f5181b87ed29f3c0211034dde17373ea84b0cea5665c43405dabd8230d8b2f8c"