Entropy pool security flaw fix and enhancements

######Security flaw fix######

• A bug was introduced where in SLASH 4.86 that the bitrate portion(output) of the Slash hash internal state was effectively erased on the first of two runs between each entropy capture/generation cycle. This has been fixed via creating a temporary instance of slash hash, feeding the current entropy pool, time and milliseconds since program was opened into this temporary instance to create an intermediate hash. This intermediate hash will then be inputted into the permanent instance(entropy producing version) of slash hash to create the final new entropy pool state.
  The security impact of this bug on entropy generation was Moderate - only affects SLASH 4.86

######Enhancements in entropy pool generation######

• Entropy pool generation now has its own module file, instead of the subroutine being contained in Start.vb(the first form that opens, giving choice between text or file encryption/decryption)

• The time for entropy generation is now captured as DateTime.UtcNow as opposed to DateTime.Now

Backwards compatible encryption/decryption with previous versions of SLASH 4.8x releases.

Please update to SLASH 4.87 due to mentioned security flaw with SLASH 4.86!

Minor Entropy capture tweak

Previously each entropy pool generation would erase the SLASH ARX hash internal state, I noticed this so I amended the entropy generation algorithm so that the SLASH hash internal state would no longer be erased with each new entropy pool generation. This will potentially make targeting potential exploits against the SLASH entropy generating algorithm much harder to perform to an attacker.

This is a minor tweak and thus encrypted data remains backwards compatible with previous SLASH 4.8x releases.

SLASH v4.85

Backwards compatible encryption/decryption with previous SLASH versions of 4.8x

Changes:

######Improved Entropy Capture######

• Mouse coordinates are now collected anywhere on the screen, not just within the application window as previous versions

• Entropy capture starts on immediate execution of program, continues throughout program execution and stops when program closes, as opposed to previous versions where entropy capture was started and stopped on Encrypt File/Text window opening/exiting.

######GUI Improvements######

• You can now finally start data encryption/decryption by pressing the enter/return button while within the password/key text entry field!

• Program message box's can no longer be spammed as opposed to previous versions, if a message appears from the program on screen the controls remain locked until the message is closed.

SLASH v4.81 - Minor bug fix and optimisation

SLASH 128 bit v4.81 - Bug fix included:

• A minor bug was fixed where 0-15 random bytes may be added to the end of decrypted files in SLASH v4.8, dependant on original data size, this was caused by 2 lines of code in the original algorithm responsible for fetching the last data block size from decrypted IV data headers. This does not cause direct data loss in the final decrypted file itself but may lead to erratic file behaviour depending on file type. In program text decryption was less impacted by this bug. To 'repair' SLASH v4.8 decrypted files, decrypt original SLASH v4.8 encrypted files/text with SLASH v4.81 or if this is not an option(eg. encrypted data file deleted) remove the added bytes from the end of the file manually via a hex editor. This bug does not affect security of already encrypted files with SLASH v4.8.

• Optimised key verification algorithm.

SLASH v4.81 is backwards compatible with SLASH v4.8 encrypted data and vice versa - but due to the bug in writing decrypted file data as described above, please use SLASH v4.81 into the future.

SLASH v4.8 release

#######Major changes made since SLASH v4.7#######

1. Changed linear feedback shift register based sponge hash function to newer and slower ARX sponge type function - Reduces attacker brute force ability of possible ciphertext keys.

2. Improved recognition method of invalid/valid keys by using pseudorandom 32 bit salt appended at end of decrypted IV block - based on hash of 96 bit IV + key to detect key matches. The last block size is also stored via xor within a random nibble(8 locations) of this 32 bit salt. This reduces the ability for attackers to use possible plain text or brute force attacks based on the old system used in previous versions due to relative salt pseudo random generation.

3. Improved IV generation - unlike previous versions that used the hash of key + milliseconds since 1970 for IV Generation, this version now uses the hash value of a 256 bit entropy pool value combined with user key for IV(initialisation vector) generation . This entropy pool collects window user mouse cords, time in 64 bit millisecond counter since window has opened and time in milliseconds since 1970 with the previous entropy pool value. This collected data is hashed together to generate a entropy pool value - this entropy pool is refreshed/regenerated 1000 times a second.

#######Note#######

Incompatible ciphertexts with SLASH v4.7 or below due to these changes in how key verification works. Please decrypt data from previous SLASH versions and encrypt with SLASH v4.8 going forward.

SLASH v4.7

Fixed minor Mix/Diffusion function bug, encrypted data with SLASH v4.65 or earlier is no longer compatible with SLASH v4.7 as a result. Please decrypt SLASH v4.65 data and re-encrypt with SLASH v4.7 moving forward.

SLASH 128 v4.65

Latest Beta release of SLASH 128