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How it works

1

Decoding

The ASCII distribution chart will use decoded ciphertext content for charting the underlying bytes of data. UTF-8, UTF-16, and UTF-32 will be converted to a byte array, and the bytes will be evaluated.
2

Ciphertext Settings

ASCII distribution takes into consideration the settings for each ciphertext. These settings currently include:
  • Ignore whitespace
  • Ignore punctuation
  • Ignore casing
  • Genericize text
This works by decoding the ciphertext and using the number that the byte represents for each byte in the sequence.
3

Frequency Calculations

After all of the above steps are performed, the frequency calculations are executed and mapped to the distribution chart.

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ASCII Distribution Settings

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Display range

The following options are given to adjust the display range of the chart. This can help focus on the relevant parts of the chart:
  • ASCII: range of 0-127. This is the standard ASCII table.
  • Extended (Default): 0-255. This is the “extended” ASCII table (latin1).
  • Input range: only displays data starting from the lowest charted byte and ending at the highest charted byte.

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Count vs. Percentage

The y-axis can be toggled to use either a count or a percentage measurement.

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Count

The count option will chart the byte frequencies in terms of raw count, and how many times they appear in the ciphertext.

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Percentage

The percentage option will chart the byte frequencies in terms of raw count divided by total byte count.

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Practical Application

ASCII distribution analysis can be leveraged to:
  • Discover if a given stream of bytes has been shifted up or down along the ASCII table.
  • Determine if two or more ciphertexts follow similar character distribution.

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Caveats

  • Use of this tool with UTF-8, UTF-16, and UTF-32 will produce mixed results, as these encodings do not use single bytes to represent characters.