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Posted 1 Jan 2019

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Effective Data Handling: Compress and Encrypt with Tango Library

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1 Jan 2019CPOL4 min read
.NET Library for in-memory GZip and LZMA compression combined with strong BlakeB based stream cipher engine

Introduction

This project introduces a self-sustained .NET library (DLL) for in-memory data (as byte array and MemoryStream) compression and encryption. Naturally, the processed output can be saved to hard drive, but the project concentrates on the effective way of in-memory data processing.

Compression

The obvious choice for the compression is in-built into .NET GZip functionality and LZM algorithm as provided by 7zip SDK C# implementation being the most effective compression function so far.

Since the purpose of the project is straight in-memory transformation, it does not provide for 7Zip files formation with their specific header structure. The library invokes GZip and LZM compression algorithms to deflate/inflate in-memory data using the parallel programming to take advantage of multiple CPU cores.

The library available compression options come from the following:

C#
public enum CompressionAlgo {
    GZip_All,
    GZip1,
    GZip2,
    GZip4,
    GZip8,
    LZMA_All,
    LZMA1,
    LZMA2,
    LZMA4,
    LZMA8,
    None
}

where 1, 2, 4, 8 stand for the number of processors to be engaged during compression and Gzip_All and LZMA_All - for all available machine processors (which usually equals to 8 so LZMA_All and LZMA8 have the same meaning).

The main and only purpose of the functionality provided is in-memory manipulation. So the single-threaded LZMA1 compression result (byte array) saved to hard drive forms the correct 7z file that can be opened with 7zip application but multi-threaded options do not provide for well-formatted 7z file.

Encryption

For the encryption part, the library introduces the fast stream cipher based on BlakeB compression function as implemented by Samuel Neves, Christian Winnerlein and Uli Riehm.

The BlakeB compression function works at the core of a generator that creates the output bytes array (pad) unique to the user in-putted key, salt and distribution values.

The produced pad is used in the following manner for the encryption/decryption:

  • Encryption: Plain text (byte array p) XOR pad => Cipher text (byte array x)
  • Decryption: Cipher text (x) XOR pad => Plain text (p)

Since encrypt and decrypt function are both just XORing the bytes with the pad, the cipher engine includes the single function Crypt covering both cases and giving us the stream cipher implementation.

Both generator (BGen class in the program) and stream cipher (Streamer class in the program) work in the parallel mode utilizing multi-core processor.

For example, if machine has 8 processors, generator will produce 8 parallel arrays and glue them into the single output (pad). Needless to say that these pieces are guaranteed to be unique and not repeating.

Similarly, Streamer will divide the input stream into 8 pieces, XOR them with the 8 corresponding parts of the pad and produce the summary result.

Let’s make some modification to the BlakeB functionality.

The core compression function consists of blocks like these:

C#
         v0 = v0 + v4 + m0;
         v12 = v12 ^ v0;
         v12 = ((v12 >> 32) | (v12 << (32)));
         v8 = v8 + v12;
         v4 = v4 ^ v8;
         v4 = ((v4 >> 24) | (v4 << (40)));
         v0 = v0 + v4 + m1;
         v12 = v12 ^ v0;
         v12 = ((v12 >> 16) | (v12 << (48)));
         v8 = v8 + v12;
         v4 = v4 ^ v8;
         v4 = ((v4 >> 63) | (v4 << (1)));

         v1 = v1 + v5 + m2;
         v13 = v13 ^ v1;
         v13 = ((v13 >> 32) | (v13 << (32)));
         v9 = v9 + v13;
         v5 = v5 ^ v9;
         v5 = ((v5 >> 24) | (v5 << (40)));
         v1 = v1 + v5 + m3;
         v13 = v13 ^ v1;
         v13 = ((v13 >> 16) | (v13 << (48)));
         v9 = v9 + v13;
         v5 = v5 ^ v9;
         v5 = ((v5 >> 63) | (v5 << (1)));
...

with repeating shift constants 32, 24, 16 and 63. Each of the constants appears 96 times in 12 rounds of processing totalling 384 times altogether.

To make the adversary’s life more interesting, current implementation initially generates byte array S[384] based on the user password (key), salt and distribution input. This allows for the following pattern in the compression function:

C#
         int i = 0;

         v0 = v0 + v4 + m0;
         v12 = v12 ^ v0;
         v12 = RR(v12, S[i++]);
         v8 = v8 + v12;
         v4 = v4 ^ v8;
         v4 = RR(v4, S[i++]);
         v0 = v0 + v4 + m1;
         v12 = v12 ^ v0;
         v12 = RR(v12, S[i++]);
         v8 = v8 + v12;
         v4 = v4 ^ v8;
         v4 = RR(v4, S[i++]);
...

where RR is the right rotation function:

C#
private ulong RR(ulong x, byte n) {

     return (x >> n) | (x << (-n & 63));
}

Thus the compression function utilizes the unique set of 384 shift numbers (bytes) dependant on user inputted key, salt and distribution eliminating arbitrary constants from the calculations.

The only constants in the Generator are programmer-defined ulongs:

C#
private const ulong IV0 =  9111111111111111111;
private const ulong IV1 =  8222222222222222222;
private const ulong IV2 =  7333333333333333333;
private const ulong IV3 =  6444444444444444444;
private const ulong IV4 =  5555555555555555555;
private const ulong IV5 =  4666666666666666666;
private const ulong IV6 =  3777777777777777777;
private const ulong IV7 =  2888888888888888888;
private const ulong IV8 =  1999999999999999999;
private const ulong IV9 =  1111111111111111111;
private const ulong IV10 = 2222222222222222222;
private const ulong IV11 = 3333333333333333333;
private const ulong IV12 = 4444444444444444444;
private const ulong IV13 = 5555555555555555555;
private const ulong IV14 = 6666666666666666666;
private const ulong IV15 = 7777777777777777777;

private const ulong FNL0 = 123456789;
private const ulong FNL1 = 987654321;

Set unique constants in your implementation and enjoy the reliable and flexible personal stream cipher where nothing is predefined externally.

The user-provided salt and distribution input affect the initial state of the Generator and therefore add to the dispersion of the outcome.

Tango Library

The Tango library's Tang class is a single entry point with interface for compression only, encryption only or both.

Here’s the constructors usage examples.

Compression

C#
Tang tang1 = new Tang(CompressionAlgo.GZip1); // use GZip on 1 processor

Tang tang2 = new Tang(CompressionAlgo.LZMA8); // use LZMA on 8 processors

Encryption

C#
Tang tang3 = new Tang("key", "salt", "distr", 1); // use 1 processor for encryption

Tang tang4 = new Tang(key, salt, distr);          // use all processors for encryption. 
                                                  // key,salt and distr are byte arrays

Encryption with Compression

C#
Tang tang5 = new Tang(CompressionAlgo.GZip8, "key",
     "salt", "distr", 4); // GZip8 compression, 4 processors for encryption

Tang tang6 = new Tang
(CompressionAlgo.LZMA1, "key", "salt", "distr"); // LZMA1 compression, 
                                                 // all processors for encryption

In Action

C#
Tang tang1 = new Tang(CompressionAlgo.GZip1);

byte[] plain = ...

byte[] compressed = tang1.Zip(plain);
byte[] uncompressed = tang1.Unzip(compressed);


Tang tang 2 = new Tang("key", "salt", "distr");

byte[] encrypted= tang2.Crypt(plain);

// The reset is needed when using the same tang object for the
// paired encrypt/decrypt and tangle/untangle actions.

tang2.Reset();

byte[] decrypted = tang2.Crypt (encrypted);


Tang tang3 = new Tang(CompressionAlgo.LZMA1, "key", "salt", "distr");

byte[] tangled = tang3.Tangle(plain);       // Tangle is Crypt(Zip(plain))

tang3.Reset();

byte[] untangled = tang3.Untangle(tangled); // Untangle is Unzip(Crypt(tangled))

Also available are Tango functions with MemoryStream input parameters instead of byte arrays.

Do not forget to put try/catch blocks around un-operations Unzip and Untangle.

Generation

After initialization, tang object can generate byte array of given length that is unique to provided key, salt and distribution:

C#
Tang tang = new Tang("key", "salt", "distr");

byte[] hash = tang.Generate(int length);

Measurements

PC: i7 2GHz 64-bit 8 cores

Tangle()

Source: 9,653,618 B (fb2 file - allows for high compression)
    time compression rate
GZip1 2,463,446 B 1259 ms 25.52%
GZip8 2,472,430 B 303 ms 25.61%
LZMA1 1,777,219 B 30995 ms 18.41%
LZMA8 1,914,649 B 6124 ms 19.83%

Compression Only

Source: 9653618 B
    time compression rate
GZip1 2,463,446 B 1169 ms 3.7% 25.52%
GZip8 2,472,430 B 293 ms 0.9% 25.61%
LZMA1 1,777,219 B 31377 ms 100% 18.41%
LZMA8 1,914,649 B 6131 ms 19.5% 19.83%

The most effective compression algo as expected is LZMA1 which comes with the highest time cost.

GZip8 is 4 times faster than GZip1 and practically not inferior in compression.

Encryption Only

Source: 9653618 B
  time  
1 core 903 ms 100%
2 cores 457 ms 50.6%
4 cores 295 ms 32.7%
8 cores 219 ms 24.3%
Generation

10,000,000 bytes generated within 250 ms

Initialization Speed
C#
Tang tang = new Tang (CompressionAlgo.LZMA8, "key", "salt", "distr");

The Tang construction time takes about 0.08 ms independently of the CompressionAlgo applied.

Take your entanglement with Tango easy!

History

  • 1st January, 2019: Initial version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


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