What's a covert writing? Steganography is a technique for hiding secret information in a common carrier. Use this tool LSB (lowest valid bit) algorithms that encode information to the lowest level of a picture pixel, with minimal modifications that the naked eye cannot detect.

Step 1: Select the carrier picture

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Click or drag PNG pictures here

The larger the size of the PNG format is recommended, the more information the size can hide

Step 2: Enter the information to hide

Secret information

Characters： 0

Required pixel bits: 0

Encrypt to protect information using XOR password

♪ The key tip: The resulting picture must be saved in PNG format. JPEG, WebP, etc., can undermine the hidden data and lead to extraction failure.

Select a picture containing hidden information

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Click or drag to write hidden pictures here

Only support PNG format (JPEG pictures are usually not correctly extracted)

Message encrypted. Password decryption required

📖 Full guide to the photo covert writing

What's a picture of the invisibility?

The hidden writing (Stegangraphy, derived from Greek "hidden writing") is an ancient technique that hides secret information in a common carrier, and unlike encryption, the object of the covert writing is not to make it "untelligible," but to keep the information "existent" undetected.

Common forms of modern digital invisibility include hiding text in pictures, embedding data in audio files, hiding information in each frame of the video.

LSB Algorithmic Principle

This tool uses the LSB algorithm (Least Significant Bit, lowest valid bit). Every pixel is by R, G, B Three colour channels are made up, each of which is expressed in 8-bit binary (0-255).

Modifying the minimum 1 bit of each channel, the effect on colour is only 1/256, and the naked eye is completely invisible. In this way, one. 1000 x 1000 pixels PNG images can hide about 375 KB text messages.

For example, pixel values 11001010 (decimal 202) Amend to read 11001011 (decimal 203) The colour changes by less than 0.4%, and the eye is not able to discern differences.

Description of data format

The data format for this tool code is:

STEG : 4 byte tag to verify whether the picture contains hidden data
8-bit length Byte length of recording messages (supports up to 9999999 bytes)
Message Contents Text content for UTF-8 encoding

XOR Encryption Protection

This tool supports XOR in addition to LSB invisibility Encryption: Before writing pixels, you use a password to vary or encrypt text, and you need to enter the same password to recreate the content. This way, even if others knew the picture was in hiding, it could not be read without a password.

XOR The advantage of encryption is that it is very fast, does not require key management and is suitable for light-weight encryption scenarios. I'd like to suggest a first-time security test. AES encrypts text, then invisibility.

Why must we use PNG?

PNG is a non-dermal compression format, guaranteed to be in the same position when pixels are saved. And JPEG Use impaired compression, with minor pixel value modification (DCT conversion) while saving, directly disrupts the hidden data in LSB.

Rules: (a) The carrier image recommends PNG; The resulting hidden picture must be saved as PNG , may not be converted to JPEG or other impaired format.

Invisible capacity calculations

The number of characters that can be hidden is ≈ pixels of the picture x 3 ÷ 8 − 12 (labelled and lengthd). Common dimensions reference:

500 x 500: approximately 93 KB Text
1920 x 1080: approximately 777 KB Text
4K (3840 x 2160): approximately 3.1 MB Text

Common application scene

Secretly transmitting sensitive contact details or passwords
Digital watermark: Embedding copyright information in pictures
Research and learning in covert writing
Release pictures with private letters on open platforms
CTF title

Security precautions

JPEG recompress, image tailor, zoom in will undermine the hidden data
The screenshot or secondary scan will lose pixel-level data.
Professional implicit analysis tool (steganalysis) can be statistically detected for LSB anomalies
High Security scene suggests supersing AES encryption

Common problems FAQ

Q: Is the picture bigger?
A: The file size is essentially the same, the LSB changes in PNG do not affect the volume of the file, but only minor changes in pixel content.

Q: Why did the extraction fail?
A: Common reason: 1 picture is converted to JPEG； 2 pictures compressed/cut; 3 Check to understand secret but password error; The four pictures were not originally hidden.

Q: Does the cell phone send pictures that destroy data?
A: Micro-Credit, QQQ, etc. will compress pictures (twisting) JPEG, it's gonna destroy the data. It is suggested that the option be sent as a "document" or as a original map.

Q: Support JPEG carriers?
A: may load JPEG as a carrier, but the result must be saved to PNG. If you save it again as JPEG, the data will be lost.

Label:

Invisibility LSB algorithm PNG Picture XOR encryption Can not open message Digital watermarks CTFtools

Image Invisibility Tool

Step 1: Select the carrier picture

Step 2: Enter the information to hide

♪ The writing is working! Message hidden in picture

Select a picture containing hidden information

- Zip, pull!