private static AggregationHashChain CreateAggregationHashChainWithLevelCorrection(AggregationHashChain aggregationHashChain, ulong levelCorrection)
{
ReadOnlyCollection <AggregationHashChain.Link> chainLinks = aggregationHashChain.GetChainLinks();
TlvTagBuilder builder = new TlvTagBuilder(aggregationHashChain);
AggregationHashChain.Link firstLink = chainLinks[0];
builder.ReplaceChildTag(firstLink, CreateLinkWithLevelCorrection(firstLink, levelCorrection));
return(new AggregationHashChain(builder.BuildTag()));
}
private static KsiSignature CreateSignatureWithLevelCorrection(KsiSignature signature, uint addToFirstLinkLinkLevelCorrection)
{
ReadOnlyCollection <AggregationHashChain> aggregationHashChains = signature.GetAggregationHashChains();
TlvTagBuilder builder = new TlvTagBuilder(signature);
AggregationHashChain firstAggregationHashChain = aggregationHashChains[0];
ulong levelCorrection = firstAggregationHashChain.GetChainLinks()[0].LevelCorrection + addToFirstLinkLinkLevelCorrection;
builder.ReplaceChildTag(firstAggregationHashChain, CreateAggregationHashChainWithLevelCorrection(firstAggregationHashChain, levelCorrection));
return(new KsiSignature(false, false, builder.GetChildTags()));
}
/// <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);
}