Security and Performance

The maximum file size that can be accommodated by Humber is 30 MB (in Hex mode the maximum plain language file size is 10 MB).  The speed of reading input files depends critically on the size of the maximum file size and the block size during the data read operations.  If larger files are required to be encrypted, the time taken to read in the data will be increased, unless the block size is also increased.

The performance tests were run on a Dell Inspiron 545 Desktop computer fitted with an Intel Core 2 Quad CPU Q8300 running at 2.5 GHz.  The computer had 4 GB RAM with a 64-bit operating system running under Windows 7.  Two test files were encrypted and decrypted.  Because the files have to be read in blocks and assigned to variables, the read time for large files becomes sufficiently significant to be measured.  On the other hand, the output is written as a single stream, so the write time is negligible.  File 1 was a binary bit map file "Dump.bmp".  File 2 was a Word file "Humber.docx".  The recorded times for encryption and decryption are shown in Table I:

  File Size Encryption Decryption
Read Time Process Time Read Time Process Time
File 1 5.12 Mb 4.3 secs 9.7 secs 4.3 secs 9.7 secs
File 2 315 kB < 0.5 sec < 0.5 sec < 0.5 sec < 0.5 sec

The recorded times do not include the time taken to carry out the random processes for the hash function, key file ID generation and message setting number, which take approximately 4 seconds in total for any encryption, but are not required for decryption.