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