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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 May 24, 2009 | |
| 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 M Ar maxmem | |
| 34 .Op Fl m Ar maxmemfrac | |
| 35 .Op Fl t Ar maxtime | |
| 36 .Ar infile | |
| 37 .Op Ar outfile | |
| 38 .Sh DESCRIPTION | |
| 39 .Nm Cm enc | |
| 40 encrypts | |
| 41 .Ar infile | |
| 42 and writes the result to | |
| 43 .Ar outfile | |
| 44 if specified, or the standard output otherwise. | |
| 45 The user will be prompted to enter a passphrase (twice) to | |
| 46 be used to generate a derived encryption key. | |
| 47 .Pp | |
| 48 .Nm Cm dec | |
| 49 decrypts | |
| 50 .Ar infile | |
| 51 and writes the result to | |
| 52 .Ar outfile | |
| 53 if specified, or the standard output otherwise. | |
| 54 The user will be prompted to enter the passphrase used at | |
| 55 encryption time to generate the derived encryption key. | |
| 56 .Sh OPTIONS | |
| 57 .Bl -tag -width "-m maxmemfrac" | |
| 58 .It Fl M Ar maxmem | |
| 59 Use at most | |
| 60 .Ar maxmem | |
| 61 bytes of RAM to compute the derived encryption key. | |
| 62 .It Fl m Ar maxmemfrac | |
| 63 Use at most the fraction | |
| 64 .Ar maxmemfrac | |
| 65 of the available RAM to compute the derived encryption key. | |
| 66 .It Fl t Ar maxtime | |
| 67 Usr at most | |
| 68 .Ar maxtime | |
| 69 seconds of CPU time to compute the derived encryption key. | |
| 70 .El | |
| 71 In | |
| 72 .Nm Cm enc , | |
| 73 the memory and CPU time limits are enforced by picking | |
| 74 appropriate parameters to the | |
| 75 .Nm | |
| 76 key derivation function. | |
| 77 In | |
| 78 .Nm Cm dec , | |
| 79 the memory and CPU time limits are enforced by exiting with | |
| 80 an error if decrypting the file would require too much memory | |
| 81 or CPU time. | |
| 82 .Sh EXIT STATUS | |
| 83 The | |
| 84 .Nm | |
| 85 utility exits 0 on success, and >0 if an error occurs. | |
| 86 .Pp | |
| 87 Note that if the input encrypted file is corrupted, | |
| 88 .Nm Cm dec | |
| 89 may produce output prior to determining that the input | |
| 90 was corrupt and exiting with a non-zero status; so | |
| 91 users should direct the output to a safe location and | |
| 92 check the exit status of | |
| 93 .Nm | |
| 94 before using the decrypted data. | |
| 95 .Sh SEE ALSO | |
| 96 .Rs | |
| 97 .%A "Colin Percival" | |
| 98 .%T "Stronger Key Derivation via Sequential Memory-Hard Functions" | |
| 99 .%O "Presented at BSDCan'09" | |
| 100 .%D "May 2009" | |
| 101 .Re | |
| 102 .Sh HISTORY | |
| 103 The | |
| 104 .Nm | |
| 105 utility was written in May 2009 by Colin Percival as a | |
| 106 demonstration of the | |
| 107 .Nm | |
| 108 key derivation function. | |
| 109 The | |
| 110 .Nm | |
| 111 key derivation function was invented in March 2009 by Colin | |
| 112 Percival in order to allow key files from the | |
| 113 .Nm tarsnap | |
| 114 backup system to be passphrase protected. | |
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