This program uses statistics on the frequency of three-letter sequences

   in English to generate passwords.  The statistics are

   generated from your dictionary by the program loadtris.

   See www.multicians.org/thvv/gpw.html for history and info.

   Tom Van Vleck

   THVV 06/01/94 Coded

   THVV 04/14/96 converted to Java

   THVV 07/30/97 fixed for Netscape 4.0

  

   You are welcome to the source, if you

    * Share your source with others freely

    * Let me know you're using it

    * Give me credit, and all the other pioneers, if you use the data or algorithms

  

   */

  int npw = 10;

  int pwl = 8;

  static GpwData data = null;

  final static String alphabet = "abcdefghijklmnopqrstuvwxyz";

  public String generate (int npw, int pwl) {

    int c1, c2, c3;

    long sum = 0;

    int nchar;

    long ranno;

    int pwnum;

    double pik;

    StringBuffer password;

    Random ran = new Random(); // new random source seeded by clock

    if (data == null) {

      data = new GpwData();

    }

    // Pick a random starting point.

    for (pwnum=0; pwnum < npw; pwnum++) {

      password = new StringBuffer(pwl);

      pik = ran.nextDouble(); // random number [0,1]

      ranno = (long)(pik * data.getSigma()); // weight by sum of frequencies

      sum = 0;

      for (c1=0; c1 < 26; c1++) {

        for (c2=0; c2 < 26; c2++) {

          for (c3=0; c3 < 26; c3++) {

            sum += data.get(c1, c2, c3);

            if (sum > ranno) {

              password.append(alphabet.charAt(c1));

              password.append(alphabet.charAt(c2));

              password.append(alphabet.charAt(c3));

              c1 = 26; // Found start. Break all 3 loops.

              c2 = 26;

              c3 = 26;

            } // if sum

          } // for c3

        } // for c2

      } // for c1

      // Now do a random walk.

      nchar = 3;

      while (nchar < pwl) {

        c1 = alphabet.indexOf(password.charAt(nchar-2));

        c2 = alphabet.indexOf(password.charAt(nchar-1));

        sum = 0;

        for (c3=0; c3 < 26; c3++)

          sum += data.get(c1, c2, c3);

        if (sum == 0) {

          break;  // exit while loop

        }

        pik = ran.nextDouble();

        ranno = (long)(pik * sum);

        sum = 0;

        for (c3=0; c3 < 26; c3++) {

          sum += data.get(c1, c2, c3);

          if (sum > ranno) {

            password.append(alphabet.charAt(c3));

            c3 = 26; // break for loop

          } // if sum

        } // for c3

        nchar ++;

      } // while nchar

      return password.toString(); // Password generated

    } // for pwnum

    return null;

  } // generate()

// ================================================================

  static short tris[][][] = null;

  static long sigma[] = null; // 125729

  GpwData () {

    int c1, c2, c3;

    tris = new short[26][26][26];

    sigma = new long[1];

    GpwDataInit1.fill(this); // Break into two classes for NS 4.0

    GpwDataInit2.fill(this); // .. its Java 1.1 barfs on methods > 65K

    for (c1=0; c1 < 26; c1++) {

      for (c2=0; c2 < 26; c2++) {

        for (c3=0; c3 < 26; c3++) {

          sigma[0] += (long) tris[c1][c2][c3];

        } // for c3

      } // for c2

    } // for c1

  } // constructor

  void set(int x1, int x2, int x3, short v) {

    tris[x1][x2][x3] = v;

  } // set()

  long get(int x1, int x2, int x3) {

    return (long) tris[x1][x2][x3];

  } // get()

  long getSigma() {

    return sigma[0];

  } // get()

// ================================================================

  final static short tris1[][][] = {{ /* [13][26][26] */

/* A A */ {2,0,3,0,0,0,1,0,0,0,0,1,1,1,0,0,0,3,2,0,0,0,0,0,0,0},