bugfix in encryption key computing, added new feature: derived public keys

tests/jot

@@ -0,0 +1,3 @@
+#!/usr/bin/perl
+my $rounds = shift;
+foreach (0 .. $rounds) {print "$_\n";}

tests/pwhashes.c

@@ -0,0 +1,54 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+#include <sodium.h>
+#include <limits.h>
+
+#include "mem.h"
+#include "defines.h"
+#include "keyprint.h"
+#include "key.h"
+
+struct _pw_t {
+  char hash[65];
+  UT_hash_handle hh;
+};
+typedef struct _pw_t pw;
+
+int main() {
+  int i, t, p;
+  char *pass = ucmalloc(4);
+  unsigned char *h;
+  char tmp[65];
+  pw *item;
+  pw *list = NULL;
+  pw *have = NULL;
+
+  for(i=97; i<126; ++i) {
+    pass[0] = i;
+    pass[1] = 0;
+    h = pcp_derivekey(pass);
+
+    p =0;
+    for(t=0; t<32; ++t) {
+      sprintf(&tmp[p], "%02x", h[t]);
+      p += 2;
+    }
+
+    have = NULL;
+    HASH_FIND_STR(list, tmp, have);
+    if(have == NULL) {
+      item = ucmalloc(sizeof(pw));
+      memcpy(item->hash, tmp, 65);
+      HASH_ADD_STR( list, hash, item ); 
+    }
+    else {
+      fprintf(stderr, "Error: collision found: %s!\n", have->hash);
+      return 1;
+    }
+  }
+
+  fprintf(stderr, "ok\n");
+  return 0;
+}