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1 | .\" Copyright 2009 Colin Percival |
2 | .\" All rights reserved. | |
3 | .\" | |
4 | .\" Redistribution and use in source and binary forms, with or without | |
5 | .\" modification, are permitted provided that the following conditions | |
6 | .\" are met: | |
7 | .\" 1. Redistributions of source code must retain the above copyright | |
8 | .\" notice, this list of conditions and the following disclaimer. | |
9 | .\" 2. Redistributions in binary form must reproduce the above copyright | |
10 | .\" notice, this list of conditions and the following disclaimer in the | |
11 | .\" documentation and/or other materials provided with the distribution. | |
12 | .\" | |
13 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND | |
14 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
15 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
16 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE | |
17 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
18 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
19 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
20 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
21 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
22 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
23 | .\" SUCH DAMAGE. | |
24 | .Dd February 10, 2017 | |
25 | .Dt SCRYPT 1 | |
26 | .Os | |
27 | .Sh NAME | |
28 | .Nm scrypt | |
29 | .Nd encrypt and decrypt files. | |
30 | .Sh SYNOPSIS | |
31 | .Nm | |
32 | .Brq Cm enc | Cm dec | |
33 | .Op Fl f | |
34 | .Op Fl M Ar maxmem | |
35 | .Op Fl m Ar maxmemfrac | |
36 | .Op Fl t Ar maxtime | |
37 | .Op Fl P | |
38 | .Ar infile | |
39 | .Op Ar outfile | |
40 | .Nm | |
41 | .Fl -version | |
42 | .Sh DESCRIPTION | |
43 | .Nm Cm enc | |
44 | encrypts | |
45 | .Ar infile | |
46 | and writes the result to | |
47 | .Ar outfile | |
48 | if specified, or the standard output otherwise. | |
49 | The user will be prompted to enter a passphrase (twice) to | |
50 | be used to generate a derived encryption key. | |
51 | .Pp | |
52 | .Nm Cm dec | |
53 | decrypts | |
54 | .Ar infile | |
55 | and writes the result to | |
56 | .Ar outfile | |
57 | if specified, or the standard output otherwise. | |
58 | The user will be prompted to enter the passphrase used at | |
59 | encryption time to generate the derived encryption key. | |
60 | .Pp | |
61 | If | |
62 | .Fl P | |
63 | is not given, | |
64 | .Nm | |
65 | reads passphrases from its controlling terminal, or failing that, | |
66 | from stdin. Prompts are only printed when | |
67 | .Nm | |
68 | is reading passphrases from some terminal. If | |
69 | .Fl P | |
70 | is given, then | |
71 | .Nm | |
72 | does not print any prompts, and reads a passphrase from stdin. | |
73 | .Sh OPTIONS | |
74 | .Bl -tag -width "-m maxmemfrac" | |
75 | .It Fl f | |
76 | Force the decryption to proceed even if it is anticipated to | |
77 | require an excessive amount of memory or CPU time. | |
78 | .It Fl M Ar maxmem | |
79 | Use at most | |
80 | .Ar maxmem | |
81 | bytes of RAM to compute the derived encryption key. | |
82 | .It Fl m Ar maxmemfrac | |
83 | Use at most the fraction | |
84 | .Ar maxmemfrac | |
85 | of the available RAM to compute the derived encryption key. | |
86 | .It Fl t Ar maxtime | |
87 | Use at most | |
88 | .Ar maxtime | |
89 | seconds of CPU time to compute the derived encryption key. | |
90 | .It Fl P | |
91 | Always read passphrase from stdin, and do so only once even | |
92 | when encrypting. | |
93 | .It Fl -version | |
94 | Print version of scrypt, and exit. | |
95 | .El | |
96 | .Pp | |
97 | In | |
98 | .Nm Cm enc , | |
99 | the memory and CPU time limits are enforced by picking | |
100 | appropriate parameters to the | |
101 | .Nm | |
102 | key derivation function. | |
103 | In | |
104 | .Nm Cm dec , | |
105 | the memory and CPU time limits are enforced by exiting with | |
106 | an error if decrypting the file would require too much memory | |
107 | or CPU time. | |
108 | .Sh EXIT STATUS | |
109 | The | |
110 | .Nm | |
111 | utility exits 0 on success, and >0 if an error occurs. | |
112 | .Pp | |
113 | Note that if the input encrypted file is corrupted, | |
114 | .Nm Cm dec | |
115 | may produce output prior to determining that the input | |
116 | was corrupt and exiting with a non-zero status; so | |
117 | users should direct the output to a safe location and | |
118 | check the exit status of | |
119 | .Nm | |
120 | before using the decrypted data. | |
121 | .Sh SEE ALSO | |
122 | .Rs | |
123 | .%A "Colin Percival" | |
124 | .%T "Stronger Key Derivation via Sequential Memory-Hard Functions" | |
125 | .%O "Presented at BSDCan'09" | |
126 | .%D "May 2009" | |
127 | .Re | |
128 | .Sh HISTORY | |
129 | The | |
130 | .Nm | |
131 | utility was written in May 2009 by Colin Percival as a | |
132 | demonstration of the | |
133 | .Nm | |
134 | key derivation function. | |
135 | The | |
136 | .Nm | |
137 | key derivation function was invented in March 2009 by Colin | |
138 | Percival in order to allow key files from the | |
139 | .Nm tarsnap | |
140 | backup system to be passphrase protected. |