sha512t2561

Usage

Overview

The md5, sha1, sha224, sha256, sha384, sha512, sha512t224, sha512t256, rmd160, skein256, skein512, and skein1024 utilities take as input a message of arbitrary length and produce as output a “fingerprint” or “message digest” of the input.

The md5sum, sha1sum, sha224sum, sha256sum, sha384sum, sha512sum, sha512t224sum, sha512t256sum, rmd160sum, skein256sum, skein512sum, and skein1024sum utilities do the same, but with command-line options and an output format that match those of their similary named GNU utilities.

The shasum utility does the same, but with command-line options and an output format that match those of the similarly named utility that ships with Perl.

In all cases, each file listed on the command line is processed separately. If no files are listed on the command line, or a file name is given as -, input is taken from stdin instead.

The utility's different modes have different output formats, but in all cases, filenames containing unprintable characters are encoded as described in vis(3) using the VIS_CSTYLE | VIS_OCTAL style.

It is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given prespecified target message digest. The SHA-224, SHA-256, SHA-384, SHA-512, RIPEMD-160, and SKEIN algorithms are intended for digital signature applications, where a large file must be “compressed” in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem such as RSA.

The MD5 and SHA-1 algorithms have been proven to be vulnerable to practical collision attacks and should not be relied upon to produce unique outputs, nor should they be used as part of a cryptographic signature scheme.

SHA-512t256 is a version of SHA-512 truncated to only 256 bits. On 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but with the same level of security. The hashes are not interchangeable.

SHA-512t224 is identical to SHA-512t256, but with the digest truncated to 224 bits.

It is recommended that all new applications use SHA-512 or SKEIN-512 instead of one of the other hash functions.

Exit status

The md5, sha1, sha224, sha256, sha384, sha512, sha512t224, sha512t256, rmd160, skein256, skein512, and skein1024 utilities exit 0 on success, 1 if at least one of the input files could not be read, and 2 if at least one file does not have the same hash as the -c option.

The md5sum, sha1sum, sha224sum, sha256sum, sha384sum, sha512sum, sha512t224sum, sha512t256sum, rmd160, skein256, skein512, skein1024 and shasum utilities exit 0 on success and 1 if at least one of the input files could not be read or, when verifying checksums, does not have the expected checksum.

Examples

Calculate the MD5 checksum of the string “Hello”.

$ md5 -s Hello
MD5 ("Hello") = 8b1a9953c4611296a827abf8c47804d7

Same as above, but note the absence of the newline character in the input string:

$ echo -n Hello | md5
8b1a9953c4611296a827abf8c47804d7

Calculate the checksum of multiple files reversing the output:

$ md5 -r /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6 /boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd /etc/rc.conf

This is almost but not quite identical to the output from GNU mode:

$ md5sum /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6  /boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd  /etc/rc.conf

Note the two spaces between hash and file name. If binary mode is requested, they are instead separated by a space and an asterisk:

$ md5sum -b /boot/loader.conf /etc/rc.conf
ada5f60f23af88ff95b8091d6d67bef6 */boot/loader.conf
d80bf36c332dc0fdc479366ec3fa44cd */etc/rc.conf

Write the digest for /boot/loader.conf in a file named digest. Then calculate the checksum again and validate it against the checksum string extracted from the digest file:

$ md5 /boot/loader.conf > digest && md5 -c $(cut -f2 -d= digest) /boot/loader.conf
MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6

Same as above but comparing the digest against an invalid string (“randomstring”), which results in a failure.

$ md5 -c randomstring /boot/loader.conf
MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6 [ Failed ]

In GNU mode, the -c option does not compare against a hash string passed as parameter. Instead, it expects a digest file, as created under the name digest for /boot/loader.conf in the example above.

$ md5sum -c digest
/boot/loader.conf: OK

The digest file may contain any number of lines in the format generated in either BSD or GNU mode. If a hash value does not match the file, “FAILED” is printed instead of “OK”.

Caveats

The encoding used for file names containing non-printable characters is incompatible with that used by GNU coreutils. The encoding used by GNU coreutils is non-reversible, in that certain non-printable characters are encoded while others are simply omitted. The encoding used by this utility, on the other hand, is fully reversible.

If interoperability with GNU coreutils is required, it is recommended to ensure that all file names contain only printable characters.

Acknowledgments

This utility was originally derived from a program which was placed in the public domain for free general use by RSA Data Security.

Support for SHA-1 and RIPEMD-160 was added by Oliver Eikemeier ⟨[email protected]⟩.

Support for SHA-2 was added by Colin Percival ⟨[email protected]⟩ and Allan Jude ⟨[email protected]⟩.

Support for SKEIN was added by Allan Jude ⟨[email protected]⟩.

Compatibility with GNU coreutils was added by Warner Losh ⟨[email protected]⟩ and much expanded by Dag-Erling Smørgrav ⟨[email protected]⟩, who also added Perl compatibility.