@c FIXME: the following need documentation
@c * [: (coreutils)[ invocation. File/string tests.
@c * pinky: (coreutils)pinky invocation. FIXME.
-@c * shasum: (coreutils)shasum invocation. Print or check message-digests.
@c * uptime: (coreutils)uptime invocation. FIXME.
@dircategory Individual utilities
* ln: (coreutils)ln invocation. Make links between files.
* logname: (coreutils)logname invocation. Print current login name.
* ls: (coreutils)ls invocation. List directory contents.
-* md5sum: (coreutils)md5sum invocation. Print or check message-digests.
+* md5sum: (coreutils)md5sum invocation. Print or check MD5 digests.
* mkdir: (coreutils)mkdir invocation. Create directories.
* mkfifo: (coreutils)mkfifo invocation. Create FIFOs (named pipes).
* mknod: (coreutils)mknod invocation. Create special files.
* rm: (coreutils)rm invocation. Remove files.
* rmdir: (coreutils)rmdir invocation. Remove empty directories.
* seq: (coreutils)seq invocation. Print numeric sequences
+* sha1sum: (coreutils)sha1sum invocation. Print or check SHA-1 digests.
+* sha2: (coreutils)sha2 utilities. Print or check SHA-2 digests.
* shred: (coreutils)shred invocation. Remove files more securely.
* sleep: (coreutils)sleep invocation. Delay for a specified time.
* sort: (coreutils)sort invocation. Sort text files.
* Output of entire files:: cat tac nl od
* Formatting file contents:: fmt pr fold
* Output of parts of files:: head tail split csplit
-* Summarizing files:: wc sum cksum md5sum
+* Summarizing files:: wc sum cksum md5sum sha1sum sha2
* Operating on sorted files:: sort uniq comm ptx tsort
* Operating on fields within a line:: cut paste join
* Operating on characters:: tr expand unexpand
* wc invocation:: Print newline, word, and byte counts.
* sum invocation:: Print checksum and block counts.
* cksum invocation:: Print CRC checksum and byte counts.
-* md5sum invocation:: Print or check message-digests.
+* md5sum invocation:: Print or check MD5 digests.
+* sha1sum invocation:: Print or check SHA-1 digests.
+* sha2 utilities:: Print or check SHA-2 digests.
Operating on sorted files
* wc invocation:: Print newline, word, and byte counts.
* sum invocation:: Print checksum and block counts.
* cksum invocation:: Print CRC checksum and byte counts.
-* md5sum invocation:: Print or check message-digests.
+* md5sum invocation:: Print or check MD5 digests.
+* sha1sum invocation:: Print or check SHA-1 digests.
+* sha2 utilities:: Print or check SHA-2 digests.
@end menu
@node md5sum invocation
-@section @command{md5sum}: Print or check message-digests
+@section @command{md5sum}: Print or check MD5 digests
@pindex md5sum
+@cindex MD5
@cindex 128-bit checksum
@cindex checksum, 128-bit
@cindex fingerprint, 128-bit
@command{md5sum} computes a 128-bit checksum (or @dfn{fingerprint} or
@dfn{message-digest}) for each specified @var{file}.
+
+Note: The MD5 digest is more reliable than a simple CRC (provided by
+the @command{cksum} command) for detecting accidental file corruption,
+as the chances of accidentally having two files with indentical MD5
+are vanishingly small. However, it should not be considered truly
+secure against malicious tampering: although finding a file with a
+given MD5 fingerprint, or modifying a file so as to retain its MD5 are
+considered infeasible at the moment, it is known how to produce
+different files with identical MD5 (a ``collision''), something which
+can be a security issue in certain contexts. For more secure hashes,
+consider using SHA-1 or SHA-2. @xref{sha1sum invocation}, and
+@ref{sha2 utilities}.
+
If a @var{file} is specified as @samp{-} or if no files are given
@command{md5sum} computes the checksum for the standard input.
@command{md5sum} can also determine whether a file and checksum are
@exitstatus
+@node sha1sum invocation
+@section @command{sha1sum}: Print or check SHA-1 digests
+
+@pindex sha1sum
+@cindex SHA-1
+@cindex 160-bit checksum
+@cindex checksum, 160-bit
+@cindex fingerprint, 160-bit
+@cindex message-digest, 160-bit
+
+@command{sha1sum} computes a 160-bit checksum for each specified
+@var{file}. The usage and options of this command are precisely the
+same as for @command{md5sum}. @xref{md5sum invocation}.
+
+Note: The SHA-1 digest is more secure than MD5, and no collisions of
+it are known (different files having the same fingerprint). However,
+it is known that they can be produced with considerable, but not
+unreasonable, resources. For this reason, it is generally considered
+that SHA-1 should be gradually phased out in favor of the more secure
+SHA-2 hash algorithms. @xref{sha2 utilities}.
+
+
+@node sha2 utilities
+@section sha2 utilities: Print or check SHA-2 digests
+
+@pindex sha224sum
+@pindex sha256sum
+@pindex sha384sum
+@pindex sha512sum
+@cindex SHA-2
+@cindex 224-bit checksum
+@cindex 256-bit checksum
+@cindex 384-bit checksum
+@cindex 512-bit checksum
+@cindex checksum, 224-bit
+@cindex checksum, 256-bit
+@cindex checksum, 384-bit
+@cindex checksum, 512-bit
+@cindex fingerprint, 224-bit
+@cindex fingerprint, 256-bit
+@cindex fingerprint, 384-bit
+@cindex fingerprint, 512-bit
+@cindex message-digest, 224-bit
+@cindex message-digest, 256-bit
+@cindex message-digest, 384-bit
+@cindex message-digest, 512-bit
+
+The commands @command{sha224sum}, @command{sha256sum},
+@command{sha384sum} and @command{sha512sum} compute checksums of
+various lengths (respectively 224, 256, 384 and 512 bits),
+collectively known as the SHA-2 hashes. The usage and options of
+these commands are precisely the same as for @command{md5sum}.
+@xref{md5sum invocation}.
+
+Note: The SHA384 and SHA512 digests are considerably slower to
+compute, especially on 32-bit computers, than SHA224 or SHA256.
+
+
@node Operating on sorted files
@chapter Operating on sorted files
projects / thirdparty / coreutils.git / commitdiff
