170 lines
7.9 KiB
HTML
170 lines
7.9 KiB
HTML
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<title>des(3) - Plan 9 from User Space</title>
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<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
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<table border=0 cellpadding=0 cellspacing=0 width=100%>
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<tr height=10><td>
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<tr><td width=20><td>
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<tr><td width=20><td><b>DES(3)</b><td align=right><b>DES(3)</b>
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<tr><td width=20><td colspan=2>
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<br>
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<p><font size=+1><b>NAME </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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setupDESstate, des_key_setup, block_cipher, desCBCencrypt, desCBCdecrypt,
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desECBencrypt, desECBdecrypt, des3CBCencrypt, des3CBCdecrypt,
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des3ECBencrypt, des3ECBdecrypt, key_setup, des56to64, des64to56,
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setupDES3state, triple_block_cipher, - single and triple digital
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encryption standard
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</table>
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<p><font size=+1><b>SYNOPSIS </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<tt><font size=+1>#include <u.h><br>
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#include <libc.h><br>
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#include <mp.h><br>
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#include <libsec.h>
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des_key_setup(uchar key[8], ulong schedule[32])
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void block_cipher(ulong *schedule, uchar *data, int decrypting)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void setupDESstate(DESstate *s, uchar key[8], uchar *ivec)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void desCBCencrypt(uchar*, int, DESstate*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void desCBCdecrypt(uchar*, int, DESstate*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void desECBencrypt(uchar*, int, DESstate*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void desECBdecrypt(uchar*, int, DESstate*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void triple_block_cipher(ulong keys[3][32], uchar*, int)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void setupDES3state(DES3state *s, uchar key[3][8], uchar *ivec)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des3CBCencrypt(uchar*, int, DES3state*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des3CBCdecrypt(uchar*, int, DES3state*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des3ECBencrypt(uchar*, int, DES3state*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des3ECBdecrypt(uchar*, int, DES3state*)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void key_setup(uchar[7], ulong[32])
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des56to64(uchar *k56, uchar *k64)
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</font></tt>
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<tt><font size=+1>void des64to56(uchar *k64, uchar *k56)<br>
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</font></tt>
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</table>
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<p><font size=+1><b>DESCRIPTION </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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The Digital Encryption Standard (DES) is a shared key or symmetric
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encryption using either a 56 bit key for single DES or three 56
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bit keys for triple des. The keys are encoded into 64 bits where
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every eight bit is parity.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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The basic DES function, <i>block_cipher</i>, works on a block of 8 bytes,
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converting them in place. It takes a key schedule, a pointer to
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the block, and a flag indicating encrypting (0) or decrypting
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(1). The key schedule is created from the key using <i>des_key_setup</i>.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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Since it is a bit awkward, <i>block_cipher</i> is rarely called directly.
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Instead, one normally uses routines that encrypt larger buffers
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of data and which may chain the encryption state from one buffer
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to the next. These routines keep track of the state of the encryption
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using a <tt><font size=+1>DESstate</font></tt> structure that contains the key
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schedule and any chained state. <i>SetupDESstate</i> sets up the <tt><font size=+1>DESstate</font></tt>
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structure using the key and an 8 byte initialization vector.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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Electronic code book, using <i>desECBencrypt</i> and <i>desECBdecrypt</i>, is
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the less secure mode. The encryption of each 8 bytes does not
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depend on the encryption of any other. Hence the encryption is
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a substitution cipher using 64 bit characters.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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Cipher block chaining mode, using <i>desCBCencrypt</i> and <i>desCBCdecrypt</i>,
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is more secure. Every block encrypted depends on the initialization
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vector and all blocks encrypted before it.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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For both CBC and ECB modes, a stream of data can be encrypted
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as multiple buffers. However, all buffers except the last must
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be a multiple of 8 bytes to ensure successful decryption of the
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stream.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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There are equivalent triple DES functions for each of the DES
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functions.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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In the past Plan 9 used a 56 bit or 7 byte format for DES keys.
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To be compatible with the rest of the world, we’ve abandoned this
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format. There are two functions: <i>des56to64</i> and <i>des64to56</i> to convert
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back and forth between the two formats. Also a key schedule can
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be set up from the 7 byte format using <i>key_setup</i>.
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<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
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</table>
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<p><font size=+1><b>SOURCE </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<tt><font size=+1>/usr/local/plan9/src/libsec<br>
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</font></tt>
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</table>
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<p><font size=+1><b>SEE ALSO </b></font><br>
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<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
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<a href="../man3/mp.html"><i>mp</i>(3)</a>, <a href="../man3/aes.html"><i>aes</i>(3)</a>, <a href="../man3/blowfish.html"><i>blowfish</i>(3)</a>, <a href="../man3/dsa.html"><i>dsa</i>(3)</a>, <a href="../man3/elgamal.html"><i>elgamal</i>(3)</a>, <a href="../man3/rc4.html"><i>rc4</i>(3)</a>, <a href="../man3/rsa.html"><i>rsa</i>(3)</a>,
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<a href="../man3/sechash.html"><i>sechash</i>(3)</a>, <a href="../man3/prime.html"><i>prime</i>(3)</a>, <a href="../man3/rand.html"><i>rand</i>(3)</a><br>
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</table>
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<td width=20>
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<tr height=20><td>
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</table>
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<!-- TRAILER -->
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<center>
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<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a>
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