/// <summary>
/// Create KSI signature instance from given signature by adding a new aggregation hash chain as the lowest level chain.
/// </summary>
/// <param name="signature">Base KSI signature</param>
/// <param name="inputHash">Input hash of the aggregation chain to be added.</param>
/// <param name="aggregationAlgorithm">Aggregation algorithm of the aggregation chain to be added.</param>
/// <param name="chainLinks">Hash chain links of the aggregation chain to be added.</param>
/// <returns></returns>
public IKsiSignature CreateSignatureWithAggregationChain(IKsiSignature signature, DataHash inputHash, HashAlgorithm aggregationAlgorithm,
AggregationHashChain.Link[] chainLinks)
{
AggregationHashChain lowestChain = signature.GetAggregationHashChains()[0];
// create chain index
ulong[] firstLevelChainIndex = lowestChain.GetChainIndex();
ulong[] chainIndex = new ulong[firstLevelChainIndex.Length + 1];
Array.Copy(firstLevelChainIndex, 0, chainIndex, 0, firstLevelChainIndex.Length);
chainIndex[chainIndex.Length - 1] = AggregationHashChain.CalcLocationPointer(chainLinks);
// Create new lowest chain
AggregationHashChain newAggregationHashChain = new AggregationHashChain(lowestChain.AggregationTime, chainIndex, inputHash, aggregationAlgorithm.Id, chainLinks);
// check level correction
AggregationHashChainResult chainResult = newAggregationHashChain.GetOutputHash(new AggregationHashChainResult(0, inputHash));
ulong levelCorrection = lowestChain.GetChainLinks()[0].LevelCorrection;
if (chainResult.Level > levelCorrection)
{
throw new KsiException(string.Format(
"The aggregation hash chain cannot be added as lowest level chain. It's output level ({0}) is bigger than level correction of the first link of the first aggregation hash chain of the base signature ({1}).",
chainResult.Level, levelCorrection));
}
if (chainResult.Hash != lowestChain.InputHash)
{
throw new KsiException("The aggregation hash chain cannot be added as lowest level chain. It's output hash does not match base signature input hash.");
}
// Create list on new signature child tags.
// Add new aggregation hash chain as the first element.
// Add the chain that was initally the lowest (with corrected level correction) as second element
List <ITlvTag> childTags = new List <ITlvTag>
{
newAggregationHashChain,
CreateAggregationHashChainWithLevelCorrection(lowestChain, levelCorrection - chainResult.Level)
};
foreach (ITlvTag tag in signature)
{
// Add all the signature components except the chain that was initially the lowest.
if (!ReferenceEquals(tag, lowestChain))
{
childTags.Add(tag);
}
}
KsiSignature resultSignature = new KsiSignature(false, false, childTags.ToArray());
Verify(resultSignature, inputHash);
return(resultSignature);
}
/// <summary>
/// Get last aggregation hash chain output hash that is calculated from all aggregation hash chains
/// </summary>
/// <returns>output hash</returns>
public DataHash GetLastAggregationHashChainRootHash()
{
if (_aggregationHashChainRootHash != null)
{
return(_aggregationHashChainRootHash);
}
AggregationHashChainResult lastResult = new AggregationHashChainResult(0, _aggregationHashChains[0].InputHash);
foreach (AggregationHashChain chain in _aggregationHashChains)
{
lastResult = chain.GetOutputHash(lastResult);
}
return(_aggregationHashChainRootHash = lastResult.Hash);
}
/// <summary>
/// Get output hash.
/// </summary>
/// <param name="result">last hashing result</param>
/// <returns>output hash chain result</returns>
public AggregationHashChainResult GetOutputHash(AggregationHashChainResult result)
{
if (result == null)
{
throw new ArgumentNullException(nameof(result));
}
lock (_cacheLock)
{
if (_aggregationHashChainResultCache == null)
{
_aggregationHashChainResultCache = new Dictionary <AggregationHashChainResult, AggregationHashChainResult>();
}
else if (_aggregationHashChainResultCache.ContainsKey(result))
{
return(_aggregationHashChainResultCache[result]);
}
}
DataHash lastHash = result.Hash;
ulong level = result.Level;
foreach (Link link in _links)
{
level += link.LevelCorrection + 1;
if (link.Direction == LinkDirection.Left)
{
lastHash = GetStepHash(lastHash.Imprint, link.GetSiblingData(), level);
}
if (link.Direction == LinkDirection.Right)
{
lastHash = GetStepHash(link.GetSiblingData(), lastHash.Imprint, level);
}
}
AggregationHashChainResult returnValue = new AggregationHashChainResult(level, lastHash);
lock (_cacheLock)
{
_aggregationHashChainResultCache[result] = returnValue;
}
return(returnValue);
}
/// <summary>
/// Compare current object against another object.
/// </summary>
/// <param name="obj">object to compare with</param>
/// <returns>true if objects are equal</returns>
public override bool Equals(object obj)
{
AggregationHashChainResult a = obj as AggregationHashChainResult;
// If parameter is null, return false.
if (ReferenceEquals(a, null))
{
return(false);
}
if (ReferenceEquals(this, a))
{
return(true);
}
// If run-time types are not exactly the same, return false.
if (GetType() != a.GetType())
{
return(false);
}
return(Hash == a.Hash && Level == a.Level);
}
