Using Zero‑Width Characters in Python for Steganography and Text Control

What Are Zero‑Width Characters

Zero‑Width Characters are Unicode symbols that occupy a position in a string but render no visible width. They are used for steganography, format control, and other text‑processing tasks.

Zero Width Non‑Joiner (U+200C)

Zero Width Joiner (U+200D)

Zero Width Space (U+200B)

Word Joiner (U+2060)

Uses of Zero‑Width Characters

Steganography: Insert invisible characters to hide information.

Avoiding automated detection: Insert characters to bypass crawlers or filters.

Text formatting control: Influence character joining in scripts such as Arabic or Hindi.

Data watermarking: Embed invisible characters as a provenance marker.

Inserting Zero‑Width Characters (Python)

# Insert a zero‑width space (U+200B)
text = "hello"
hidden_text = text[0] + "\u200B" + text[1:]
print("Original text:", text)          # Original text: hello
print("Text with zero‑width space:", hidden_text)  # Appears as hello but contains a hidden character
print("Contains zero‑width space:", "\u200B" in hidden_text)  # True

Hiding and Extracting Information (Python)

def hide_message(base_text, hidden_message):
    """Encode hidden_message into base_text using zero‑width spaces"""
    zero_width_space = "\u200B"
    binary_message = ''.join(format(ord(c), '08b') for c in hidden_message)
    encoded_message = ''.join(zero_width_space if bit == '1' else '' for bit in binary_message)
    return base_text + encoded_message

def extract_message(base_text, encoded_text):
    """Extract hidden_message from encoded_text"""
    zero_width_space = "\u200B"
    hidden_binary = ''.join('1' if ch == zero_width_space else '0' for ch in encoded_text)
    chars = [chr(int(hidden_binary[i:i+8], 2)) for i in range(0, len(hidden_binary), 8) if hidden_binary[i:i+8]]
    return base_text + ''.join(chars)

base_text = "This is a test."
hidden_message = "Hi"
encoded_text = hide_message(base_text, hidden_message)
print("Encoded text:", encoded_text)
extracted_message = extract_message(base_text, encoded_text)
print("Extracted text:", extracted_message)

Bypassing String Detection (Python)

# Simulate a sensitive‑word filter
def contains_sensitive_word(text, sensitive_word):
    return sensitive_word in text

sensitive_word = "secret"
modified_text = sensitive_word[0] + "\u200B" + sensitive_word[1:]
print("Contains sensitive word:", contains_sensitive_word(modified_text, sensitive_word))  # False

Removing Zero‑Width Characters (Python)

def remove_zero_width_chars(text):
    """Remove all zero‑width characters from text"""
    zero_width_chars = ['\u200B', '\u200C', '\u200D', '\u2060']
    for ch in zero_width_chars:
        text = text.replace(ch, '')
    return text

text_with_zero_width = "hello\u200Bworld\u200C!"
cleaned_text = remove_zero_width_chars(text_with_zero_width)
print("Original:", text_with_zero_width)
print("Cleaned:", cleaned_text)

Zero‑width characters are powerful for text processing, steganography, and data marking, but they should be used cautiously in security‑sensitive contexts.