Concealment

/ˌɪnfərˈmeɪʃən ˈhaɪdɪŋ/

noun — "concealing data within other data."

Information Hiding is the practice of embedding or concealing data within other digital media or systems in a way that prevents its detection by casual observers. Unlike encryption, which makes content unreadable without a key, information hiding focuses on secrecy by making the presence of the data itself inconspicuous. It is widely used in steganography, digital watermarking, software design, and secure communication systems to protect sensitive content, verify ownership, or maintain privacy.

Technically, digital information hiding exploits redundant, imperceptible, or low-significance components of the carrier medium. In images, this often involves modifying the least significant bits (LSBs) of pixel values to encode hidden data without perceptible visual changes. In audio or video, imperceptible frequency alterations, phase shifts, or timing variations can embed information. In software engineering, information hiding refers to encapsulating implementation details of modules or classes, exposing only necessary interfaces to reduce complexity and prevent misuse.

Operationally, embedding hidden information involves selecting a carrier, encoding the payload using a specific algorithm, and transmitting or storing the carrier. Extraction requires knowledge of the embedding method or key, depending on the approach. For example, using LSB steganography in an image:

# Example: hide one bit in a grayscale pixel
pixel = 200          # original pixel value
bit_to_hide = 1      # bit to embed
pixel = (pixel & 0b11111110) | bit_to_hide
print(pixel)         # outputs 201

In software engineering, information hiding is implemented via encapsulation: internal data structures are hidden, and access is controlled through well-defined interfaces. This reduces unintended dependencies and improves maintainability and security.

In practice, information hiding underpins steganography for covert messaging, digital watermarking for copyright protection, and secure system design for software modularity. It is also applied in network protocols to conceal control information, embed metadata, or track digital content. Detection or analysis of hidden data often requires steganalysis, signal analysis, or code inspection.

Conceptually, information hiding is like placing a message inside a sealed, opaque envelope within a stack of ordinary letters: the letter itself appears normal, but those with the correct method can access the hidden content without raising suspicion.

See Steganography, Steganalysis, Digital Watermarking, LSB, Encryption.

/ˌstɛɡəˈnɒɡrəfi/

noun — "hidden communication within digital media."

Steganography is the practice of concealing information within another medium so that the presence of the hidden message is not detectable to casual observers. Unlike cryptography, which focuses on making data unreadable to unauthorized parties, steganography emphasizes secrecy by embedding information in a way that appears innocuous or ordinary. Common digital mediums include images, audio files, video streams, and text documents.

Technically, digital steganography works by manipulating redundant or less noticeable elements in the carrier file. For example, in images, the least significant bits (LSBs) of pixel values can encode hidden data without perceptibly altering the image. In audio, inaudible frequency bands or phase shifts may carry information. In text, spacing, font variations, or invisible characters can encode messages. The size of the hidden payload and the choice of embedding algorithm affect detectability and robustness. Techniques range from simple LSB insertion to advanced methods using error correction, encryption, and spread spectrum encoding.

Operationally, sending a steganographic message involves selecting a carrier file, applying an embedding algorithm to hide the payload, and transmitting the carrier over a standard channel. The recipient, knowing the method and keys if applicable, extracts the hidden data. Tools like Steghide or OpenPuff automate embedding and extraction in images and audio. For example:

steghide embed -cf image.jpg -ef secret.txt -p password
steghide extract -sf image.jpg -p password

This sequence hides secret.txt inside image.jpg using a password and later retrieves it without altering the image's visible content.

In practice, steganography is used for confidential communication, watermarking digital media, embedding metadata, and digital rights management. Security applications may combine cryptography with steganography to protect sensitive information further. Detection of steganography, called steganalysis, involves statistical analysis of carrier files to identify anomalies caused by embedded data.

Conceptually, steganography is like writing a secret note in invisible ink on a postcard: the postcard itself appears normal, but those with the correct method can reveal the hidden message, ensuring covert communication.

See Cryptography, Steganalysis, Digital Watermarking, LSB, Encryption.