hashing {openssl} | R Documentation

## Vectorized hash/hmac functions

### Description

All hash functions either calculate a hash-digest for `key == NULL` or HMAC (hashed message authentication code) when `key` is not `NULL`. Supported inputs are binary (raw vector), strings (character vector) or a connection object.

### Usage

    sha1(x, key = NULL)

    sha224(x, key = NULL)

    sha256(x, key = NULL)

    sha384(x, key = NULL)

    sha512(x, key = NULL)

    sha2(x, size = 256, key = NULL)

    md4(x, key = NULL)

    md5(x, key = NULL)

    blake2b(x, key = NULL)

    blake2s(x, key = NULL)

    ripemd160(x, key = NULL)

### Arguments

`x` | character vector, raw vector or connection object.
`key` | string or raw vector used as the key for HMAC hashing
`size` | must be equal to 224 256 384 or 512

### Details

Functions are vectorized for the case of character vectors: a vector with `n` strings returns `n` hashes. When passing a connection object, the contents will be stream-hashed which minimizes the amount of required memory. This is recommended for hashing files from disk or network.

The sha2 family of algorithms (sha224, sha256, sha384 and sha512) is generally recommended for sensitive information. While sha1 and md5 are usually sufficient for collision-resistant identifiers, they are no longer considered secure for cryptographic purposes.

In applications where hashes should be irreversible (such as names or passwords) it is often recommended to use a random key for HMAC hashing. This prevents attacks where we can lookup hashes of common and/or short strings. See examples. A common special case is adding a random salt to a large number of records to test for uniqueness within the dataset, while simultaneously rendering the results incomparable to other datasets.

The `blake2b` and `blake2s` algorithms are only available if your system has libssl 1.1 or newer.

### References

Digest types: https://www.openssl.org/docs/manmaster/man1/dgst.html

### Examples

    # Support both strings and binary
    md5(c("foo", "bar"))
    md5("foo", key = "secret")

    hash <- md5(charToRaw("foo"))
    as.character(hash, sep = ":")

    # Compare to digest
    digest::digest("foo", "md5", serialize = FALSE)

    # Other way around
    digest::digest(cars, skip = 0)
    md5(serialize(cars, NULL))

    # Stream-verify from connections (including files)
    myfile <- system.file("CITATION")
    md5(file(myfile))
    md5(file(myfile), key = "secret")

    ## Not run: check md5 from: http://cran.r-project.org/bin/windows/base/old/3.1.1/md5sum.txt
    md5(url("http://cran.r-project.org/bin/windows/base/old/3.1.1/R-3.1.1-win.exe"))
    ## End(Not run)

    # Use a salt to prevent dictionary attacks
    sha1("admin") # googleable
    sha1("admin", key = "random_salt_value") #not googleable

    # Use a random salt to identify duplicates while anonymizing values
    sha256("john") # googleable
    sha256(c("john", "mary", "john"), key = "random_salt_value")

[Package openssl version 0.9.7 Index]