compression, encryption + hashing

compression, encryption + hashing

1. COMPRESSION

   • lossy
     • reduces the file size by permanently removing some of its information.
       • image, video + audio files
       • decrease in quality, inability to return to the original format
   • lossless
     • compressed files by recording patterns in data instead of the actual data the original file can be recovered from the compressed version.
       • text files, source code, bank statements
       • doesn't reduce file size as much as lossy does
     • dictionary encoding
       • frequently occurring pieces of data are replaced by smaller groups of indexes when being transferred.
         • A dictionary is then used to say which indexes match which groups of characters.
           • When decompressed the dictionary is used to replace the tokens with the original text
     • RLE
       • repeated values are removed and replaced with one occurrence of the data followed by the number of times it should be repeated.

2. ENCRYPTION

   • process of converting plaintext into cipher text