ECC.pas

   1 unit ECC;
   2
   3 INTERFACE
   4 uses ed25519,Sha1;
   5 type tEccKey=ed25519.tKey32;
   6 type tPoWTimeStamp=Word;
   7
   8 var SecretKey:ed25519.tKey64;
   9 var PublicKey:tEccKey;
  10 var PublicPoW:tEccKey;
  11 var PublicPoWTS:Word;
  12 var ZeroDigest:tSha1Digest;
  13 const cDig3PowMask=%0010;
  14 const cPoWValidWeeks=1;
  15 const cWeekDays=5;
  16 const cWeekEpoch=40179;
  17 procedure CreateChallenge(out Challenge: tEccKey);
  18 procedure CreateResponse(const Challenge: tEccKey; out Response: tSha1Digest; const srce:tEccKey);
  19 function VerifyPoW(const proof:tEccKey; const RemotePub:tEccKey; const stamp:Word):boolean;
  20
  21 operator :=(k:tEccKey) s:string;
  22
  23 IMPLEMENTATION
  24 uses SysUtils,StrUtils,DateUtils;
  25
  26 procedure CreateChallenge(out Challenge: tEccKey);
  27  var i:byte;
  28  begin
  29  for i:=0 to 31 do challenge[i]:=Random(256);
  30 end;
  31
  32 procedure CreateResponse(const Challenge: tEccKey; out Response: tSha1Digest; const srce:tEccKey);
  33  var Shared:tEccKey;
  34  var shactx:tSha1Context;
  35  begin
  36  ed25519.SharedSecret(shared,srce,secretkey);
  37  Sha1Init(shactx);
  38  Sha1Update(shactx,challenge,sizeof(challenge));
  39  Sha1Update(shactx,shared,sizeof(shared));
  40  Sha1Final(shactx,Response);
  41 end;
  42
  43 var week:Word;
  44
  45 function VerifyPoW(const proof:tEccKey; const RemotePub:tEccKey; const stamp:Word):boolean;
  46  var shactx:tSha1Context;
  47  var digest:tSha1Digest;
  48  begin
  49  if abs(Week-BEtoN(stamp))<=cPoWValidWeeks then begin
  50  Sha1Init(shactx);
  51  Sha1Update(shactx,proof,sizeof(proof));
  52  Sha1Update(shactx,RemotePub,sizeof(RemotePub));
  53  Sha1Update(shactx,stamp,sizeof(stamp));
  54  Sha1Final(shactx,digest);
  55  result:=(CompareByte(digest,ZeroDigest,3)=0)and((digest[3]and cDig3PoWMask)=0);
  56  end else result:=false;
  57 end;
  58
  59 const cPoWFN='proof.dat';
  60 procedure PoWLoadFromFile;
  61  var f:file of byte;
  62  begin
  63  assign(f,cPoWFN);
  64  reset(f,1);
  65  blockread(f,PublicPoW,sizeof(PublicPoW));
  66  blockread(f,PublicPoWTS,2);
  67  close(f);
  68 end;
  69 procedure PoWGenerate;
  70  var f:file of byte;
  71  var i:byte;
  72  var counter:LongWord;
  73  var start:tDateTime;
  74  begin
  75  assign(f,cPoWFN);
  76  rewrite(f,1);
  77  write('ECC: Generating PoW, this may take a while...');
  78  PublicPowTS:=NtoBE(Week);
  79  Start:=Now; counter:=0;
  80  repeat
  81   for i:=0 to 31 do PublicPoW[i]:=Random(256);
  82   inc(counter);
  83  until VerifyPoW(PublicPoW,PublicKey,PublicPoWTS);
  84  writeln(' PoW found in ',(Now-start)*SecsPerDay:1:0,'s speed=',counter/((Now-start)*SecsPerDay):1:0,'h/s');
  85  blockwrite(f,PublicPoW,sizeof(PublicPoW));
  86  blockwrite(f,PublicPoWTS,sizeof(PublicPoWTS));
  87  close(f);
  88 end;
  89
  90 const cSeckeyFN='secret.dat';
  91 procedure LoadFromFile;
  92  var f:file of ed25519.tPrivKey;
  93  begin
  94  assign(f,cSecKeyFN);
  95  reset(f);
  96  read(f,SecretKey);
  97  close(f);
  98 end;
  99
 100 procedure SaveGenerated;
 101  var f:file of ed25519.tPrivKey;
 102  begin
 103  assign(f,cSecKeyFN);
 104  rewrite(f);
 105  //fpchmod
 106  write(f,SecretKey);
 107  close(f);
 108 end;
 109
 110 procedure Generate;
 111  {$IFDEF UNIX}
 112  var f:file of ed25519.tPrivKey;
 113  begin
 114  assign(f,'/dev/urandom');
 115  reset(f);
 116  read(f,SecretKey);
 117  close(f);
 118  {$ELSE}
 119  begin
 120  {$WARNING Not enough Random in windows license key}
 121  {$ERROR This unit requires UNIX-compatile operating system}
 122  {$ENDIF}
 123 end;
 124
 125 procedure DerivePublic;
 126  begin
 127  CreatekeyPair(PublicKey,SecretKey);
 128 end;
 129
 130 operator :=(k:tEccKey) s:string;
 131  begin
 132  Setlength(s,64);
 133  BinToHex(@k,@s[1],32);
 134 end;
 135
 136 BEGIN
 137  FillChar(ZeroDigest,sizeof(ZeroDigest),0);
 138  week:=trunc((Now-cWeekEpoch)/cWeekDays);
 139  //writeln('ECC: Today is W',Week);
 140  try LoadFromFile;
 141  except on e:Exception do begin
 142   writeln('ECC: '+e.message+' while loading secret key');
 143   Generate;
 144   (*until (PublicKey[31]=0)and(PublicKey[30]=0);*)
 145   SaveGenerated;
 146   writeln('ECC: random secret key saved to '+cSecKeyFN);
 147  end end;
 148  DerivePublic;
 149  writeln('ECC: pubkey is ',string(PublicKey));
 150  try
 151   PoWLoadFromFile;
 152   if not VerifyPoW(PublicPoW,PublicKey,PublicPoWTS)
 153    then raise eXception.Create('invalid or expired proof');
 154   if (week-BEtoN(PublicPowTS))>=cPoWValidWeeks
 155    then raise eXception.Create('proof about to expire');
 156  except on e:Exception do begin
 157   writeln('ECC: '+e.message+' while loading proof');
 158   PoWGenerate;
 159  end end;
 160  writeln('ECC: ProofOfWork valid for W',BEtoN(PublicPowTS));
 161 END.