How to using entropy analysis in ctf and reverse engineering
- Step 1Drop the challenge binary or memory dump — Upload the file. Entropy is computed per 256-byte chunk and plotted as a line chart with the full file offset on the x-axis.
- Step 2Find entropy anomalies — Look for spikes or plateaus well above or below the baseline. A spike in the middle of a text file signals embedded binary data; a valley in a compressed archive may indicate a cleartext header.
- Step 3Calculate the byte offset and carve — Use the chart's x-axis chunk index × 256 to calculate the raw file offset. Open the file in a hex editor or use dd to carve that region for further analysis.
Frequently asked questions
What chunk size does the analyzer use?+
256 bytes per chunk. This provides enough granularity to locate multi-kilobyte payloads without generating thousands of chart points for large files.
Can it find PNG chunks inside a JPEG?+
A PNG embedded in a JPEG will appear as a high-entropy spike (the IDAT compressed data) against the lower JPEG entropy baseline. Correlation with the hex inspector confirms the embedded signature.
What entropy value indicates uncompressed code?+
x86 machine code typically sits around 5.5–6.5 bits/byte. ARM thumb code is denser, often 6.5–7.0. Pure assembly text or Python bytecode sits lower, around 4.5–5.5.
Privacy first
Every JAD Security operation runs entirely in your browser. Files, passwords, and PGP private keys never leave your device — verified by zero outbound network requests during processing.