Hide It in the Last Bit — TechKnowSurge

About this interactive

The Steganography lesson hides a message inside a picture. A picture is made of pixels, and each pixel has a red, a green and a blue value, 8 bits each. Changing the leftmost bit of a value changes the color a lot, and someone would notice. Changing the last bit, the least significant one, makes no visible difference. To hide a bit, set the value's last bit to it and leave the other seven bits alone. If the last bit is already the bit you want to hide, the value does not change at all. A pixel's three values can carry three hidden bits, one each. To read the message back, take the last bit of each value, in order, and chain them together. The lesson also hides the word secret in a paragraph, as the first letter of every second word. Once you know the rule, the hidden word reads straight off the text. That is the trade-off the lesson draws: steganography alone is easy to overlook, but anyone who knows a message is there, and how it was hidden, can read it.

What you'll learn

Hide a bit in a color value by setting its least significant bit, and tell when the value stays the same
Read hidden bits back out of the last bits of a pixel's color values, and a hidden word out of a sentence by the rule it was hidden with

Aligned to

CompTIA Security+

1.4 Explain the importance of using appropriate cryptographic solutions.

NIST NICE

K0884 Knowledge of covert communication tools and techniques

Key terms

Steganography: The practice of concealing a message within another medium, such as an image or sentence, so its existence is hidden rather than its content scrambled.
Least Significant Bit: The lowest-value bit in a binary number, located at the far right, whose modification causes the smallest possible change to the overall value and is used in steganography to embed hidden data with minimal perceptible alteration.
Pixel: The smallest addressable unit of a digital image, whose color is encoded as binary values representing red, green, and blue channel intensities; display resolution is expressed as a grid of pixels.
Bit: Short for binary digit, the smallest unit of data in computing, holding a single value of 0 or 1; all digital information is ultimately composed of bits.

Topics

Steganography Least Significant Bit Interactive Fill In

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