mdw@git.distorted.org.uk Git - ezmlm/blob - surfpcs.3

   1 .TH surfpcs 3
   2 .SH NAME
   3 surfpcs \- SURF protected counter sums
   4 .SH SYNTAX
   5 .B #include <surfpcs.h>
   6
   7 void \fBsurfpcs_init\fP(&\fIs\fR,\fIseed\fR);
   8
   9 void \fBsurfpcs_add\fP(&\fIs\fR,\fIbuf\fR,\fIlen\fR);
  10
  11 void \fBsurfpcs_out\fP(&\fIs\fR,\fIh\fR);
  12
  13 surfpcs \fIs\fR;
  14 .br
  15 uint32 \fIseed\fR[32];
  16 .br
  17 unsigned char *\fIbuf\fR;
  18 .br
  19 unsigned int \fIlen\fR;
  20 .br
  21 unsigned char \fIh\fR[SURFPCS_LEN];
  22 .SH DESCRIPTION
  23 .B surfpcs
  24 converts a character string to a 256-bit output,
  25 under control of a 1024-bit seed.
  26 When the seed is secret,
  27 .B surfpcs
  28 appears to be indistinguishable from a completely random
  29 variable-length-to-256-bit function.
  30
  31 Applying
  32 .B surfpcs
  33 takes three steps.
  34 First, initialize a
  35 .B surfpcs
  36 variable,
  37 .IR s ,
  38 with
  39 .BR surfpcs_init .
  40 The seed will be recorded inside
  41 .IR s .
  42
  43 Second, feed the input to
  44 .BR surfpcs_add .
  45 .I buf
  46 is a pointer to
  47 .I len
  48 characters of input.
  49 You can split the input across any number of
  50 .B surfpcs_add
  51 calls.
  52
  53 Third, call
  54 .BR surfpcs_out .
  55 The output will be placed into
  56 .IR h ,
  57 an array of
  58 .B SURFPCS_LEN
  59 bytes.
  60 .B SURFPCS_LEN
  61 is 32.
  62
  63 To apply
  64 .B surfpcs
  65 to another input you must call
  66 .B surfpcs_init
  67 again.
  68 .SH "SEE ALSO"
  69 surf(3)