Cryptology embraces two branche: Cryptanalysis & Cryptography

6 mains concepts of cryptography:

**Confidentiality/Secrecy**: Only the destination can read the message**Authentication**: The destination can be sure the message is sent by the sender**Integrity**: The message cannot be changed during the transmission**Source nonrepudiation**: The source cannot deny sending the message**Destination nonrepudiation**: The destination cannot deny receiving the message**Signatures**: Third parties can be sure that the message is sent by the sender

- OCR recognition
- text: segmentation of characters
- sound, image, text, understanding, logic,
unfakable

human ability

Find false randomness (not a proof to true randomness)

- entropy
- compression
- chi-square
- arithmetic mean
- montecarlo estimation for PI
- serial correlation coefficient)

https://www.fourmilab.ch/random/

Example: Entropy = 7.980627 bits per character.

```
Optimum compression would reduce the size
of this 51768 character file by 0 percent.
Chi square distribution for 51768 samples is 1542.26, and randomly
would exceed this value less than 0.01 percent of the times.
Arithmetic mean value of data bytes is 125.93 (127.5 = random).
Monte Carlo value for Pi is 3.169834647 (error 0.90 percent).
Serial correlation coefficient is 0.004249 (totally uncorrelated = 0.0).
```

- requires redundancy in different instruction sets
- equivalent instructions to encode some bits
- used also as watermarking (weak stealth so bad steganography - average robustness)

aims to cloak the malicious code

```
xor [si], si
```

It xors the address si

with its value and write the result in place of the old value.
Cryptographically weak

Steganography is the practice of concealing a file, message, image, or video within another file, message, image, or video.

- false positive (under-approximation)
- false negative (over-approximation)

AV software aims != triaging files aims So it might be better to have false positive / false negative