Skip to main content

​
How it works

1

Encoding and byte source

The widget uses the ciphertext’s decoded binary data to calculate bitstream variance. The decoded binary data is calculated based on the encoding of the ciphertext.
2

Ciphertext Settings

Bitstream Variance takes into consideration the settings for each ciphertext. These settings currently include:
  • Ignore whitespace
  • Ignore punctuation
  • Ignore casing
  • Genericize text
For data encodings (base64, hex, octal, decimal, etc.) the ciphertext is first decoded to Latin-1 before the toggles are applied.
3

Bytes to bits

The decoded byte array is converted to a single stream of bits, MSB first within each byte.Example: the byte 0xA5 (165) becomes the bit sequence 1,0,1,0,0,1,0,1.
4

Bit chunk size

You choose n from 1 to 16. Each group of n bits is turned into one plotted value:
  • n = 1: each bit is one value (0 or 1).
  • n = 8: each byte is one value (0–255).
  • n = 16: each pair of bytes is one value (0–65,535).
The y-axis maximum is 2^n − 1 (e.g. 255 for n=8, 65,535 for n=16).
5

Sliding vs block mode

Sliding (overlapping): A window of n bits moves one bit at a time. Consecutive values overlap by n−1 bits. Only full n-bit windows produce a point; the last incomplete window is skipped.Block (non-overlapping): The bitstream is split into consecutive chunks of n bits. If the last chunk has fewer than n bits, it is padded using the remainder setting before being converted to one value.
6

Remainder padding (block mode only)

When the total number of bits is not divisible by n, the last block is shorter than n. You choose how to extend it to n bits before converting to decimal:
SettingMeaningExample (n=4, last bits 10)
Left pad with 0Zeros on the left0010 → 2
Right pad with 0Zeros on the right1000 → 8
Left pad with 1Ones on the left1110 → 14
Right pad with 1Ones on the right1011 → 11
In sliding mode there is no remainder value; only full windows are plotted.
7

Bits to decimal

Each n-bit chunk is interpreted as an unsigned integer in big-endian order (first bit is the most significant).Examples (n=4):
  • 0010 → 2
  • 1111 → 15
  • 1010 → 10
For n=16, 0000000100000001 → 257.
8

Plot the line

The sequence of decimal values is plotted as a line chart:
  • X-axis: Index of the value (0, 1, 2, …).
  • Y-axis: Decimal value (0 up to 2^n − 1).
Each selected ciphertext is one line, colored by its ciphertext color. Multiple ciphertexts are overlaid with a legend.

​
Bitstream Variance settings

​
Bit chunk size (n)

Number of bits per value, from 1 to 16. Larger n gives fewer points and a larger possible range (up to 65,535 for n=16).

​
N-gram mode

  • Sliding: Overlapping n-bit windows; no remainder.
  • Block: Non-overlapping n-bit chunks; remainder is padded using the option below.

​
Remainder padding

Used only in block mode when the bitstream length is not a multiple of n. Choose how to pad the last, shorter chunk:
  • Left pad with 0 / Right pad with 0 — pad with zeros.
  • Left pad with 1 / Right pad with 1 — pad with ones.
Sliding mode ignores this setting.

​
Practical application

Bitstream Variance helps you:
  • See alternating patterns. Regular up–down movement can suggest periodic structure (e.g. LFSR, repeated key, or sine-like modulation).
  • Compare ciphertexts. Overlaying lines for several inputs can show shared or different bit-level structure.
  • Inspect raw data. For hex/base64-decoded material, the plot reflects how byte (or multi-byte) values change along the stream, using the ciphertext’s decoded binary data.

​
Caveats

  • Sliding vs block change the plot. Sliding gives more points and overlapping structure; block gives one value per n bits. Use the mode that matches the structure you care about.
  • Remainder affects only the last value. In block mode, the padding choice changes only the final point. For long streams the effect is small; for very short ones it can be noticeable.
  • Large n on short text. With n=16 and very few bytes, you get only a handful of points, so the line may look flat or sparse.