Add audio steganography with LSB and spread spectrum modes
Implement two audio embedding modes following the same multi-factor authentication pipeline as image steganography (passphrase + PIN + optional RSA key + optional channel key): - audio_lsb: High-capacity LSB embedding in PCM samples for lossless formats (WAV/FLAC). Uses ChaCha20-keyed sample index selection. - audio_spread: Direct-sequence spread spectrum (DSSS) with ChaCha20- keyed bipolar chip codes, Reed-Solomon error correction, and 3-copy majority-voted length headers. Designed to survive lossy compression. New files: - audio_steganography.py: LSB embed/extract on PCM samples - spread_steganography.py: Spread spectrum embed/extract - audio_utils.py: Format detection, transcoding, validation helpers - tests/test_audio.py: 22 tests covering both modes end-to-end Updated encode.py, decode.py, cli.py (audio-encode/audio-decode commands), constants.py, models.py, exceptions.py, validation.py, __init__.py, and pyproject.toml ([audio] extra). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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adlee-was-taken
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tests/test_audio.py
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tests/test_audio.py
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"""
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Tests for Stegasoo audio steganography.
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Tests cover:
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- Audio LSB roundtrip (encode + decode)
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- Audio MDCT roundtrip (encode + decode)
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- Wrong credentials fail to decode
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- Capacity calculations
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- Format detection
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- Audio validation
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"""
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import io
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import numpy as np
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import pytest
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import soundfile as sf
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from stegasoo.constants import (
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EMBED_MODE_AUDIO_LSB,
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EMBED_MODE_AUDIO_SPREAD,
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)
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from stegasoo.models import AudioCapacityInfo, AudioEmbedStats, AudioInfo
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# =============================================================================
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# FIXTURES
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# =============================================================================
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@pytest.fixture
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def carrier_wav() -> bytes:
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"""Generate a small test WAV file (1 second, 44100 Hz, mono, 16-bit)."""
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sample_rate = 44100
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duration = 1.0
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num_samples = int(sample_rate * duration)
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# Generate a simple sine wave
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t = np.linspace(0, duration, num_samples, endpoint=False)
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samples = (np.sin(2 * np.pi * 440 * t) * 16000).astype(np.int16)
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buf = io.BytesIO()
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sf.write(buf, samples, sample_rate, format="WAV", subtype="PCM_16")
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buf.seek(0)
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return buf.read()
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@pytest.fixture
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def carrier_wav_stereo() -> bytes:
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"""Generate a stereo test WAV file."""
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sample_rate = 44100
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duration = 1.0
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num_samples = int(sample_rate * duration)
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t = np.linspace(0, duration, num_samples, endpoint=False)
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left = (np.sin(2 * np.pi * 440 * t) * 16000).astype(np.int16)
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right = (np.sin(2 * np.pi * 880 * t) * 16000).astype(np.int16)
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samples = np.column_stack([left, right])
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buf = io.BytesIO()
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sf.write(buf, samples, sample_rate, format="WAV", subtype="PCM_16")
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buf.seek(0)
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return buf.read()
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@pytest.fixture
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def carrier_wav_long() -> bytes:
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"""Generate a longer WAV (15 seconds) for spread spectrum tests."""
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sample_rate = 44100
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duration = 15.0
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num_samples = int(sample_rate * duration)
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t = np.linspace(0, duration, num_samples, endpoint=False)
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# Mix of frequencies for better MDCT embedding
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samples = (
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(np.sin(2 * np.pi * 440 * t) + np.sin(2 * np.pi * 880 * t) + np.sin(2 * np.pi * 1320 * t))
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* 5000
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).astype(np.int16)
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buf = io.BytesIO()
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sf.write(buf, samples, sample_rate, format="WAV", subtype="PCM_16")
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buf.seek(0)
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return buf.read()
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@pytest.fixture
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def carrier_wav_spread_integration() -> bytes:
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"""Generate a very long WAV (150 seconds) for spread spectrum integration tests.
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Spread spectrum needs 1024 samples per bit. With encryption + RS overhead (~690 bytes),
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we need at least 690*8*1024 = 5.7M samples ~ 130 seconds at 44.1kHz.
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"""
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sample_rate = 44100
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duration = 150.0
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num_samples = int(sample_rate * duration)
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t = np.linspace(0, duration, num_samples, endpoint=False)
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samples = (
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(np.sin(2 * np.pi * 440 * t) + np.sin(2 * np.pi * 880 * t) + np.sin(2 * np.pi * 1320 * t))
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* 5000
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).astype(np.int16)
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buf = io.BytesIO()
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sf.write(buf, samples, sample_rate, format="WAV", subtype="PCM_16")
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buf.seek(0)
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return buf.read()
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@pytest.fixture
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def reference_photo() -> bytes:
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"""Generate a small reference photo (PNG)."""
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from PIL import Image
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img = Image.new("RGB", (100, 100), color=(128, 64, 32))
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buf = io.BytesIO()
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img.save(buf, "PNG")
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buf.seek(0)
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return buf.read()
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# =============================================================================
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# AUDIO LSB TESTS
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# =============================================================================
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class TestAudioLSB:
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"""Tests for audio LSB steganography."""
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def test_calculate_capacity(self, carrier_wav):
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from stegasoo.audio_steganography import calculate_audio_lsb_capacity
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capacity = calculate_audio_lsb_capacity(carrier_wav)
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assert capacity > 0
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# 1 second at 44100 Hz mono should give ~5KB capacity at 1 bit/sample
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assert capacity > 4000
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def test_embed_extract_roundtrip(self, carrier_wav):
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"""Test basic LSB embed/extract roundtrip."""
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from stegasoo.audio_steganography import embed_in_audio_lsb, extract_from_audio_lsb
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payload = b"Hello, audio steganography!"
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# Prepend with magic header to simulate real usage pattern
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key = b"\x42" * 32
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stego_audio, stats = embed_in_audio_lsb(payload, carrier_wav, key)
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assert isinstance(stats, AudioEmbedStats)
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assert stats.embed_mode == EMBED_MODE_AUDIO_LSB
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assert stats.bytes_embedded > 0
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assert stats.samples_modified > 0
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assert 0 < stats.capacity_used <= 1.0
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# Extract
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extracted = extract_from_audio_lsb(stego_audio, key)
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assert extracted is not None
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assert extracted == payload
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def test_embed_extract_stereo(self, carrier_wav_stereo):
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"""Test LSB roundtrip with stereo audio."""
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from stegasoo.audio_steganography import embed_in_audio_lsb, extract_from_audio_lsb
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payload = b"Stereo test message"
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key = b"\xAB" * 32
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stego_audio, stats = embed_in_audio_lsb(payload, carrier_wav_stereo, key)
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assert stats.channels == 2
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extracted = extract_from_audio_lsb(stego_audio, key)
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assert extracted == payload
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def test_wrong_key_fails(self, carrier_wav):
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"""Test that wrong key produces no valid extraction."""
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from stegasoo.audio_steganography import embed_in_audio_lsb, extract_from_audio_lsb
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payload = b"Secret message"
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correct_key = b"\x42" * 32
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wrong_key = b"\xFF" * 32
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stego_audio, _ = embed_in_audio_lsb(payload, carrier_wav, correct_key)
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extracted = extract_from_audio_lsb(stego_audio, wrong_key)
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# Should return None or garbage (not the original message)
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assert extracted is None or extracted != payload
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def test_two_bits_per_sample(self, carrier_wav):
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"""Test embedding with 2 bits per sample."""
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from stegasoo.audio_steganography import embed_in_audio_lsb, extract_from_audio_lsb
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payload = b"Two bits per sample test"
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key = b"\x55" * 32
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stego_audio, stats = embed_in_audio_lsb(payload, carrier_wav, key, bits_per_sample=2)
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extracted = extract_from_audio_lsb(stego_audio, key, bits_per_sample=2)
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assert extracted == payload
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def test_generate_sample_indices(self):
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"""Test deterministic sample index generation."""
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from stegasoo.audio_steganography import generate_sample_indices
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key = b"\x42" * 32
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indices1 = generate_sample_indices(key, 10000, 100)
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indices2 = generate_sample_indices(key, 10000, 100)
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# Same key should produce same indices
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assert indices1 == indices2
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# All indices should be valid
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assert all(0 <= i < 10000 for i in indices1)
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# No duplicates
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assert len(set(indices1)) == len(indices1)
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# =============================================================================
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# AUDIO SPREAD SPECTRUM TESTS
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# =============================================================================
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class TestAudioSpread:
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"""Tests for audio spread spectrum steganography."""
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def test_calculate_capacity(self, carrier_wav_long):
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from stegasoo.spread_steganography import calculate_audio_spread_capacity
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capacity = calculate_audio_spread_capacity(carrier_wav_long)
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assert isinstance(capacity, AudioCapacityInfo)
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assert capacity.usable_capacity_bytes > 0
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assert capacity.embed_mode == EMBED_MODE_AUDIO_SPREAD
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def test_spread_roundtrip(self, carrier_wav_long):
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"""Test spread spectrum embed/extract roundtrip."""
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from stegasoo.spread_steganography import (
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embed_in_audio_spread,
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extract_from_audio_spread,
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)
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payload = b"Spread test"
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seed = b"\x42" * 32
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stego_audio, stats = embed_in_audio_spread(payload, carrier_wav_long, seed)
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assert isinstance(stats, AudioEmbedStats)
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assert stats.embed_mode == EMBED_MODE_AUDIO_SPREAD
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extracted = extract_from_audio_spread(stego_audio, seed)
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assert extracted is not None
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assert extracted == payload
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def test_wrong_seed_fails(self, carrier_wav_long):
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"""Test that wrong seed produces no valid extraction."""
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from stegasoo.spread_steganography import (
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embed_in_audio_spread,
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extract_from_audio_spread,
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)
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payload = b"Secret spread"
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correct_seed = b"\x42" * 32
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wrong_seed = b"\xFF" * 32
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stego_audio, _ = embed_in_audio_spread(payload, carrier_wav_long, correct_seed)
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extracted = extract_from_audio_spread(stego_audio, wrong_seed)
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assert extracted is None or extracted != payload
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# =============================================================================
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# FORMAT DETECTION TESTS
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# =============================================================================
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class TestFormatDetection:
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"""Tests for audio format detection."""
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def test_detect_wav(self, carrier_wav):
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from stegasoo.audio_utils import detect_audio_format
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assert detect_audio_format(carrier_wav) == "wav"
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def test_detect_unknown(self):
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from stegasoo.audio_utils import detect_audio_format
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assert detect_audio_format(b"not audio data") == "unknown"
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def test_detect_empty(self):
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from stegasoo.audio_utils import detect_audio_format
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assert detect_audio_format(b"") == "unknown"
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# =============================================================================
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# AUDIO INFO TESTS
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# =============================================================================
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class TestAudioInfo:
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"""Tests for audio info extraction."""
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def test_get_wav_info(self, carrier_wav):
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from stegasoo.audio_utils import get_audio_info
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info = get_audio_info(carrier_wav)
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assert isinstance(info, AudioInfo)
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assert info.sample_rate == 44100
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assert info.channels == 1
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assert info.format == "wav"
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assert abs(info.duration_seconds - 1.0) < 0.1
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def test_get_stereo_info(self, carrier_wav_stereo):
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from stegasoo.audio_utils import get_audio_info
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info = get_audio_info(carrier_wav_stereo)
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assert info.channels == 2
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# =============================================================================
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# VALIDATION TESTS
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# =============================================================================
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class TestAudioValidation:
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"""Tests for audio validation."""
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def test_validate_valid_audio(self, carrier_wav):
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from stegasoo.audio_utils import validate_audio
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result = validate_audio(carrier_wav)
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assert result.is_valid
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def test_validate_empty_audio(self):
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from stegasoo.audio_utils import validate_audio
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result = validate_audio(b"")
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assert not result.is_valid
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def test_validate_invalid_audio(self):
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from stegasoo.audio_utils import validate_audio
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result = validate_audio(b"not audio data at all")
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assert not result.is_valid
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def test_validate_audio_embed_mode(self):
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from stegasoo.validation import validate_audio_embed_mode
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assert validate_audio_embed_mode("audio_lsb").is_valid
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assert validate_audio_embed_mode("audio_spread").is_valid
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assert validate_audio_embed_mode("audio_auto").is_valid
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assert not validate_audio_embed_mode("invalid").is_valid
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# =============================================================================
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# INTEGRATION TESTS
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# =============================================================================
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class TestIntegration:
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"""End-to-end integration tests using encode_audio/decode_audio."""
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def test_lsb_encode_decode(self, carrier_wav, reference_photo):
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from stegasoo.decode import decode_audio
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from stegasoo.encode import encode_audio
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stego_audio, stats = encode_audio(
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message="Hello from audio steganography!",
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reference_photo=reference_photo,
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carrier_audio=carrier_wav,
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passphrase="test words here now",
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pin="123456",
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embed_mode="audio_lsb",
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)
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assert len(stego_audio) > 0
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result = decode_audio(
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stego_audio=stego_audio,
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reference_photo=reference_photo,
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passphrase="test words here now",
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pin="123456",
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embed_mode="audio_lsb",
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)
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assert result.is_text
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assert result.message == "Hello from audio steganography!"
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def test_lsb_wrong_credentials(self, carrier_wav, reference_photo):
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from stegasoo.decode import decode_audio
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from stegasoo.encode import encode_audio
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stego_audio, _ = encode_audio(
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message="Secret",
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reference_photo=reference_photo,
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carrier_audio=carrier_wav,
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passphrase="correct horse battery staple",
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pin="123456",
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embed_mode="audio_lsb",
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)
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with pytest.raises(Exception):
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decode_audio(
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stego_audio=stego_audio,
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reference_photo=reference_photo,
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passphrase="wrong passphrase words here",
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pin="654321",
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embed_mode="audio_lsb",
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)
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def test_spread_encode_decode(self, carrier_wav_spread_integration, reference_photo):
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"""Test full spread spectrum encode/decode pipeline."""
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from stegasoo.decode import decode_audio
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from stegasoo.encode import encode_audio
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stego_audio, stats = encode_audio(
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message="Spread integration test",
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reference_photo=reference_photo,
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carrier_audio=carrier_wav_spread_integration,
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passphrase="test words here now",
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pin="123456",
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embed_mode="audio_spread",
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)
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result = decode_audio(
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stego_audio=stego_audio,
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reference_photo=reference_photo,
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passphrase="test words here now",
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pin="123456",
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embed_mode="audio_spread",
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)
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assert result.message == "Spread integration test"
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def test_auto_detect_lsb(self, carrier_wav, reference_photo):
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"""Test auto-detection finds LSB encoded audio."""
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from stegasoo.decode import decode_audio
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from stegasoo.encode import encode_audio
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stego_audio, _ = encode_audio(
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message="Auto-detect test",
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reference_photo=reference_photo,
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carrier_audio=carrier_wav,
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passphrase="test words here now",
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pin="123456",
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embed_mode="audio_lsb",
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)
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result = decode_audio(
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stego_audio=stego_audio,
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reference_photo=reference_photo,
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passphrase="test words here now",
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pin="123456",
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embed_mode="audio_auto",
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)
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assert result.message == "Auto-detect test"
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