Signature compression

The usual data compression methods, applied to each signature on its own, give poor results when you store a large number of signatures. That is exactly where the PKI SDK method works best.

Compressing each signature on its own finds little redundancy. Taken as a set, though, stored signatures are highly redundant: CRLs, certificates and other structures repeat across many signatures made in a similar period.

With the SDK's signature compression, you can reach compression rates above 90%.

Compressing a signature

The @Lacuna.Pki.Cades.CadesSignatureCompression class compresses signatures. Its compression and decompression methods use an implementation of @Lacuna.Pki.Stores.ISimpleStore, which stores the data that tends to be shared among signatures. The code below compresses a signature and detaches its encapsulated content:

// bytes of a CAdES signature to compress
byte[] sigContent = ...

// Simple store backed by the file system, in the temporary directory
var store = new FileSystemSimpleStore(Path.GetTempPath());

byte[] eContent;

// Compressing the signature, with the eContent detached
byte[] compressed = CadesSignatureCompression.Compress(sigContent, store, out eContent);

// Decompressing the signature
byte[] decompressed = CadesSignatureCompression.Decompress(compressed, store, eContent);

if (sigContent.SequenceEqual(decompressed)) {
    Console.WriteLine("OK!");
} else {
    Console.WriteLine("NOT OK!");
}

The @Lacuna.Pki.Stores.ISimpleStore object is central to signature compression. The example above uses a @Lacuna.Pki.Stores.FileSystemSimpleStore, which stores the compression data in the directory passed to its constructor. To use other storage, such as a database or cloud servers, implement the @Lacuna.Pki.Stores.ISimpleStore interface.

Compressing a signature​

See also​

Compressing a signature

See also