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using System;
using System.Collections.Generic;
namespace Org.BouncyCastle.Pqc.Crypto.Lms
{
public static class Hss
{
public static HssPrivateKeyParameters GenerateHssKeyPair(HssKeyGenerationParameters parameters)
{
//
// LmsPrivateKey can derive and hold the public key so we just use an array of those.
//
LmsPrivateKeyParameters[] keys = new LmsPrivateKeyParameters[parameters.Depth];
LmsSignature[] sig = new LmsSignature[parameters.Depth - 1];
byte[] rootSeed = new byte[32];
parameters.Random.NextBytes(rootSeed);
byte[] I = new byte[16];
parameters.Random.NextBytes(I);
//
// Set the HSS key up with a valid root LMSPrivateKeyParameters and placeholders for the remaining LMS keys.
// The placeholders pass enough information to allow the HSSPrivateKeyParameters to be properly reset to an
// index of zero. Rather than repeat the same reset-to-index logic in this static method.
//
byte[] zero = new byte[0];
long hssKeyMaxIndex = 1;
for (int t = 0; t < keys.Length; t++)
{
var lms = parameters.GetLmsParameters(t);
if (t == 0)
{
keys[t] = new LmsPrivateKeyParameters(
lms.LMSigParameters,
lms.LMOtsParameters,
0,
I,
1 << lms.LMSigParameters.H,
rootSeed,
isPlaceholder: false);
}
else
{
keys[t] = new LmsPrivateKeyParameters(
lms.LMSigParameters,
lms.LMOtsParameters,
-1,
zero,
1 << lms.LMSigParameters.H,
zero,
isPlaceholder: true);
}
hssKeyMaxIndex <<= lms.LMSigParameters.H;
}
// if this has happened we're trying to generate a really large key
// we'll use MAX_VALUE so that it's at least usable until someone upgrades the structure.
if (hssKeyMaxIndex == 0)
{
hssKeyMaxIndex = long.MaxValue;
}
return new HssPrivateKeyParameters(
parameters.Depth,
new List<LmsPrivateKeyParameters>(keys),
new List<LmsSignature>(sig),
0, hssKeyMaxIndex);
}
/**
* Increments an HSS private key without doing any work on it.
* HSS private keys are automatically incremented when when used to create signatures.
* <p/>
* The HSS private key is ranged tested before this incrementation is applied.
* LMS keys will be replaced as required.
*
* @param keyPair
*/
public static void IncrementIndex(HssPrivateKeyParameters keyPair)
{
lock (keyPair)
{
RangeTestKeys(keyPair);
keyPair.IncIndex();
keyPair.GetKeys()[keyPair.L - 1].IncIndex();
}
}
public static void RangeTestKeys(HssPrivateKeyParameters keyPair)
{
lock (keyPair)
{
if (keyPair.GetIndex() >= keyPair.IndexLimit)
{
throw new Exception(
"hss private key" +
((keyPair.IsShard()) ? " shard" : "") +
" is exhausted");
}
int L = keyPair.L;
int d = L;
var prv = keyPair.GetKeys();
while (prv[d - 1].GetIndex() == 1 << prv[d - 1].GetSigParameters().H)
{
if (--d == 0)
throw new Exception("hss private key" + (keyPair.IsShard() ? " shard" : "") +
" is exhausted the maximum limit for this HSS private key");
}
while (d < L)
{
keyPair.ReplaceConsumedKey(d++);
}
}
}
public static HssSignature GenerateSignature(HssPrivateKeyParameters keyPair, byte[] message)
{
LmsSignedPubKey[] signed_pub_key;
LmsPrivateKeyParameters nextKey;
int L = keyPair.L;
lock (keyPair)
{
RangeTestKeys(keyPair);
var keys = keyPair.GetKeys();
var sig = keyPair.GetSig();
nextKey = keyPair.GetKeys()[L - 1];
// Step 2. Stand in for sig[L-1]
int i = 0;
signed_pub_key = new LmsSignedPubKey[L - 1];
while (i < L - 1)
{
signed_pub_key[i] = new LmsSignedPubKey(sig[i], keys[i + 1].GetPublicKey());
++i;
}
//
// increment the index.
//
keyPair.IncIndex();
}
LmsContext context = nextKey.GenerateLmsContext().WithSignedPublicKeys(signed_pub_key);
context.BlockUpdate(message, 0, message.Length);
return GenerateSignature(L, context);
}
public static HssSignature GenerateSignature(int L, LmsContext context)
{
return new HssSignature(L - 1, context.SignedPubKeys, Lms.GenerateSign(context));
}
public static bool VerifySignature(HssPublicKeyParameters publicKey, HssSignature signature, byte[] message)
{
int Nspk = signature.GetlMinus1();
if (Nspk + 1 != publicKey.L)
return false;
LmsSignature[] sigList = new LmsSignature[Nspk + 1];
LmsPublicKeyParameters[] pubList = new LmsPublicKeyParameters[Nspk];
for (int i = 0; i < Nspk; i++)
{
sigList[i] = signature.GetSignedPubKeys()[i].GetSignature();
pubList[i] = signature.GetSignedPubKeys()[i].GetPublicKey();
}
sigList[Nspk] = signature.Signature;
LmsPublicKeyParameters key = publicKey.LmsPublicKey;
for (int i = 0; i < Nspk; i++)
{
LmsSignature sig = sigList[i];
byte[] msg = pubList[i].ToByteArray();
if (!Lms.VerifySignature(key, sig, msg))
{
return false;
}
try
{
key = pubList[i];
}
catch (Exception ex)
{
throw new Exception(ex.Message, ex);
}
}
return Lms.VerifySignature(key, sigList[Nspk], message);
}
}
}
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