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| 125 | magnus | 1 | .\" Hey, EMACS: -*- nroff -*- |
| 2 | .\" First parameter, NAME, should be all caps |
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| 3 | .\" Second parameter, SECTION, should be 1-8, maybe w/ subsection |
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| 4 | .\" other parameters are allowed: see man(7), man(1) |
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| 5 | .TH NETTLE\-PBKDF2 1 "June 2014" "Nettle 3.0" "Nettle tools" |
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| 6 | .\" Please adjust this date whenever revising the manpage. |
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| 7 | .SH NAME |
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| 8 | nettle\-pbkdf2 \- Command-line password-based key derivation tool. |
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| 9 | .SH SYNOPSIS |
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| 10 | .B nettle\-pbkdf2 |
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| 11 | .RI [ OPTIONS ] |
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| 12 | .I SALT |
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| 13 | .SH DESCRIPTION |
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| 14 | This manual page documents briefly the |
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| 15 | .B nettle\-pbkdf2 |
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| 16 | command. |
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| 17 | This manual page was written for the Debian GNU/Linux distribution |
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| 18 | because the original program does not have a manual page. |
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| 19 | .PP |
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| 20 | .\" TeX users may be more comfortable with the \fB<whatever>\fP and |
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| 21 | .\" \fI<whatever>\fP escape sequences to invode bold face and italics, |
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| 22 | .\" respectively. |
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| 23 | \fBnettle\-pbkdf2\fP is a front-end for Nettle's PBKDF2 |
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| 24 | (Password-Based Key Derivation Function 2) implementation. PBKDF2 |
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| 25 | applies a pseudo-random function to a passphrase together with a salt, |
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| 26 | producing a \fIderived key\fP of arbitrary length. By iterating the |
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| 27 | process many times, feeding the output of each round as the input of |
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| 28 | the next, brute-force cracking of the password is made to take |
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| 29 | correspondingly longer time. The use of a salt makes it harder to use |
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| 30 | dictionaries or rainbow tables. As computers become more powerful, the |
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| 31 | number of iterations can be increased without changing the rest of the |
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| 32 | algorithm. |
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| 33 | .PP |
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| 34 | The pseudo-random function used by this tool is currently HMAC-SHA256. |
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| 35 | .PP |
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| 36 | The password is read from standard input and the resulting derived key |
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| 37 | is written to standard output in groups of 16 hexadecimal digits, |
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| 38 | unless the \-\-raw option is used. The salt and number of iterations |
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| 39 | are not included in the output. |
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| 40 | .SH OPTIONS |
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| 41 | This program follows the usual GNU command line syntax, with long |
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| 42 | options starting with two dashes (`-'). A summary of options is |
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| 43 | included below. |
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| 44 | .TP |
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| 45 | .B \-l, \-\-length=\fIlength\fP |
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| 46 | Desired output length in octets. |
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| 47 | .TP |
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| 48 | .B \-\-raw |
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| 49 | Output derived key in raw binary format. |
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| 50 | .TP |
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| 51 | .B \-\-hex-salt |
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| 52 | Specifies that \fISALT\fP is provided in hexadecimal format. |
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| 53 | .TP |
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| 54 | .B \-\-help |
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| 55 | Show summary of options. |
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| 56 | .TP |
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| 57 | .B \-V, \-\-version |
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| 58 | Show version of program. |
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| 59 | .SH SEE ALSO |
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| 60 | .BR mkpasswd (1) , |
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| 61 | .IR https://en.wikipedia.org/wiki/PBKDF2 |
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| 62 | .SH AUTHOR |
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| 63 | This manual page was originally written by Magnus Holmgren <holmgren@debian.org>, |
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| 64 | for the Debian GNU/Linux system (but may be used by others). |