tgenrandom.c - plan9port - [fork] Plan 9 from user space
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       ---
       tgenrandom.c (1171B)
       ---
            1 #include "os.h"
            2 #include <mp.h>
            3 #include <libsec.h>
            4 
            5 typedef struct State{
            6         QLock                lock;
            7         int                seeded;
            8         uvlong                seed;
            9         DES3state        des3;
           10 } State;
           11 static State x917state;
           12 
           13 static void
           14 X917(uchar *rand, int nrand)
           15 {
           16         int i, m, n8;
           17         uvlong I, x;
           18 
           19         /* 1. Compute intermediate value I = Ek(time). */
           20         I = nsec();
           21         triple_block_cipher(x917state.des3.expanded, (uchar*)&I, 0); /* two-key EDE */
           22 
           23         /* 2. x[i] = Ek(I^seed);  seed = Ek(x[i]^I); */
           24         m = (nrand+7)/8;
           25         for(i=0; i<m; i++){
           26                 x = I ^ x917state.seed;
           27                 triple_block_cipher(x917state.des3.expanded, (uchar*)&x, 0);
           28                 n8 = (nrand>8) ? 8 : nrand;
           29                 memcpy(rand, (uchar*)&x, n8);
           30                 rand += 8;
           31                 nrand -= 8;
           32                 x ^= I;
           33                 triple_block_cipher(x917state.des3.expanded, (uchar*)&x, 0);
           34                 x917state.seed = x;
           35         }
           36 }
           37 
           38 static void
           39 X917init(void)
           40 {
           41         int n;
           42         uchar mix[128];
           43         uchar key3[3][8];
           44         ulong *ulp;
           45 
           46         ulp = (ulong*)key3;
           47         for(n = 0; n < sizeof(key3)/sizeof(ulong); n++)
           48                 ulp[n] = truerand();
           49         setupDES3state(&x917state.des3, key3, nil);
           50         X917(mix, sizeof mix);
           51         x917state.seeded = 1;
           52 }
           53 
           54 void
           55 genrandom(uchar *p, int n)
           56 {
           57         qlock(&x917state.lock);
           58         if(x917state.seeded == 0)
           59                 X917init();
           60         X917(p, n);
           61         qunlock(&x917state.lock);
           62 }