xref: /freebsd/sbin/md5/md5.1 (revision 31ba4ce8898f9dfa5e7f054fdbc26e50a599a6e3)
1.\" $FreeBSD$
2.Dd June 29, 2021
3.Dt MD5 1
4.Os
5.Sh NAME
6.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 , sha512t256 , rmd160 ,
7.Nm skein256 , skein512 , skein1024 ,
8.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum , sha512sum ,
9.Nm sha512t256sum , rmd160sum , skein256sum , skein512sum , skein1024sum
10.Nd calculate a message-digest fingerprint (checksum) for a file
11.Sh SYNOPSIS
12.Nm
13.Op Fl pqrtx
14.Op Fl c Ar string
15.Op Fl s Ar string
16.Op Ar
17.Pp
18.Nm md5sum
19.Op Fl pqrtx
20.Op Fl c Ar file
21.Op Fl s Ar string
22.Op Ar
23.Pp
24(All other hashes have the same options and usage.)
25.Sh DESCRIPTION
26The
27.Nm md5 , sha1 , sha224 , sha256 , sha384 , sha512 , sha512t256 , rmd160 ,
28.Nm skein256 , skein512 ,
29and
30.Nm skein1024
31utilities take as input a message of arbitrary length and produce as
32output a
33.Dq fingerprint
34or
35.Dq message digest
36of the input.
37The
38.Nm md5sum , sha1sum , sha224sum , sha256sum , sha384sum , sha512sum ,
39.Nm sha512t256sum , rmd160sum , skein256sum , skein512sum ,
40and
41.Nm skein1024sum
42utilities do the same, but default to the reversed format of
43the
44.Fl r
45flag.
46It is conjectured that it is computationally infeasible to
47produce two messages having the same message digest, or to produce any
48message having a given prespecified target message digest.
49The SHA-224 , SHA-256 , SHA-384 , SHA-512, RIPEMD-160,
50and SKEIN
51algorithms are intended for digital signature applications, where a
52large file must be
53.Dq compressed
54in a secure manner before being encrypted with a private
55(secret)
56key under a public-key cryptosystem such as RSA.
57.Pp
58The MD5 and SHA-1 algorithms have been proven to be vulnerable to practical
59collision attacks and should not be relied upon to produce unique outputs,
60.Em nor should they be used as part of a cryptographic signature scheme.
61As of 2017-03-02, there is no publicly known method to
62.Em reverse
63either algorithm, i.e., to find an input that produces a specific
64output.
65.Pp
66SHA-512t256 is a version of SHA-512 truncated to only 256 bits.
67On 64-bit hardware, this algorithm is approximately 50% faster than SHA-256 but
68with the same level of security.
69The hashes are not interchangeable.
70.Pp
71It is recommended that all new applications use SHA-512 or SKEIN-512
72instead of one of the other hash functions.
73.Pp
74The following options may be used in any combination and must
75precede any files named on the command line.
76The hexadecimal checksum of each file listed on the command line is printed
77after the options are processed.
78.Bl -tag -width indent
79.It Fl b
80Make the
81.Nm -sum
82programs separate hash and digest with a blank followed by an asterisk instead
83of by 2 blank characters for full compatibility with the output generated by the
84coreutils versions of these programs.
85.It Fl c Ar string
86If the program was called with a name that does not end in
87.Nm sum ,
88compare the digest of the file against this string.
89.Pq Note that this option is not yet useful if multiple files are specified.
90.It Fl c Ar file
91If the program was called with a name that does end in
92.Nm sum ,
93the file passed as argument must contain digest lines generated by the same
94digest algorithm with or without the
95.Fl r
96option
97.Pq i.e. in either classical BSD format or in GNU coreutils format .
98A line with the file name followed by a colon
99.Dq ":"
100and either OK or FAILED is written for each well-formed line in the digest file.
101If applicable, the number of failed comparisons and the number of lines that were
102skipped since they were not well-formed are printed at the end.
103The
104.Fl q
105option can be used to quiesce the output unless there are mismatched entries in
106the digest.
107.Pp
108.It Fl s Ar string
109Print a checksum of the given
110.Ar string .
111.It Fl p
112Echo stdin to stdout and append the checksum to stdout.
113.It Fl q
114Quiet mode \(em only the checksum is printed out.
115Overrides the
116.Fl r
117option.
118.It Fl r
119Reverses the format of the output.
120This helps with visual diffs.
121Does nothing
122when combined with the
123.Fl ptx
124options.
125.It Fl t
126Run a built-in time trial.
127For the
128.Nm -sum
129versions, this is a nop for compatibility with coreutils.
130.It Fl x
131Run a built-in test script.
132.El
133.Sh EXIT STATUS
134The
135.Nm md5 , sha1 , sha224 , sha256 , sha512 , sha512t256 , rmd160 ,
136.Nm skein256 , skein512 ,
137and
138.Nm skein1024
139utilities exit 0 on success,
1401 if at least one of the input files could not be read,
141and 2 if at least one file does not have the same hash as the
142.Fl c
143option.
144.Sh EXAMPLES
145Calculate the MD5 checksum of the string
146.Dq Hello .
147.Bd -literal -offset indent
148$ md5 -s Hello
149MD5 ("Hello") = 8b1a9953c4611296a827abf8c47804d7
150.Ed
151.Pp
152Same as above, but note the absence of the newline character in the input
153string:
154.Bd -literal -offset indent
155$ echo -n Hello | md5
1568b1a9953c4611296a827abf8c47804d7
157.Ed
158.Pp
159Calculate the checksum of multiple files reversing the output:
160.Bd -literal -offset indent
161$ md5 -r /boot/loader.conf /etc/rc.conf
162ada5f60f23af88ff95b8091d6d67bef6 /boot/loader.conf
163d80bf36c332dc0fdc479366ec3fa44cd /etc/rc.conf
164.Pd
165The
166.Nm -sum
167variants put 2 blank characters between hash and file name for full compatibilty
168with the coreutils versions of these commands.
169.Ed
170.Pp
171Write the digest for
172.Pa /boot/loader.conf
173in a file named
174.Pa digest .
175Then calculate the checksum again and validate it against the checksum string
176extracted from the
177.Pa digest
178file:
179.Bd -literal -offset indent
180$ md5 /boot/loader.conf > digest && md5 -c $(cut -f2 -d= digest) /boot/loader.conf
181MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6
182.Ed
183.Pp
184Same as above but comparing the digest against an invalid string
185.Pq Dq randomstring ,
186which results in a failure.
187.Bd -literal -offset indent
188$ md5 -c randomstring /boot/loader.conf
189MD5 (/boot/loader.conf) = ada5f60f23af88ff95b8091d6d67bef6 [ Failed ]
190.Ed
191.Pp
192If invoked with a name ending in
193.Nm -sum
194the
195.Fl c
196option does not compare against a hash string passed as parameter.
197Instead, it expects a digest file, as created under the name
198.Pa digest
199for
200.Pa /boot/loader.conf
201in the example above.
202.Bd -literal -offset indent
203$ md5 -c digest /boot/loader.conf
204/boot/loader.conf: OK
205.Ed
206.Pp
207The digest file may contain any number of lines in the format generated with or without the
208.Fl r
209option
210.Pq i.e. in either classical BSD format or in GNU coreutils format .
211If a hash value does not match the file, FAILED is printed instead of OK.
212.Sh SEE ALSO
213.Xr cksum 1 ,
214.Xr md5 3 ,
215.Xr ripemd 3 ,
216.Xr sha 3 ,
217.Xr sha256 3 ,
218.Xr sha384 3 ,
219.Xr sha512 3 ,
220.Xr skein 3
221.Rs
222.%A R. Rivest
223.%T The MD5 Message-Digest Algorithm
224.%O RFC1321
225.Re
226.Rs
227.%A J. Burrows
228.%T The Secure Hash Standard
229.%O FIPS PUB 180-2
230.Re
231.Rs
232.%A D. Eastlake and P. Jones
233.%T US Secure Hash Algorithm 1
234.%O RFC 3174
235.Re
236.Pp
237RIPEMD-160 is part of the ISO draft standard
238.Qq ISO/IEC DIS 10118-3
239on dedicated hash functions.
240.Pp
241Secure Hash Standard (SHS):
242.Pa http://csrc.nist.gov/cryptval/shs.html .
243.Pp
244The RIPEMD-160 page:
245.Pa http://www.esat.kuleuven.ac.be/~bosselae/ripemd160.html .
246.Sh BUGS
247All of the utilities that end in
248.Sq sum
249are intended to be compatible with the GNU coreutils programs.
250However, the long option functionality is not provided.
251.Sh ACKNOWLEDGMENTS
252This program is placed in the public domain for free general use by
253RSA Data Security.
254.Pp
255Support for SHA-1 and RIPEMD-160 has been added by
256.An Oliver Eikemeier Aq Mt eik@FreeBSD.org .
257