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Cap RSA at 3072 bits, add zstd compression for QR codes

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- RSA key size capped at 3072 bits (4096 too large for QR codes)
- Added zstd compression for QR code RSA keys (better ratio than zlib)
- New prefix STEGASOO-ZS: for zstd, backward compatible with STEGASOO-Z: (zlib)
- Added zstandard dependency to web/api/compression extras
- Updated all docs, CLI options, and web UI to reflect 3072 max
- Version bump to 4.2.0

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Aaron D. Lee
2026-01-09 23:30:31 -05:00
parent 175362ce4c
commit 3fd3204552
13 changed files with 118 additions and 39 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
frontends/cli/main.py
View File

@@ -236,7 +236,7 @@ def format_channel_status_line(quiet: bool = False) -> str | None:
help=f"PIN length (6-9, default: {DEFAULT_PIN_LENGTH})",
)
@click.option(
"--rsa-bits", type=click.Choice(["2048", "3072", "4096"]), default="2048", help="RSA key size"
"--rsa-bits", type=click.Choice(["2048", "3072"]), default="2048", help="RSA key size"
)
@click.option(
"--words",
@@ -261,7 +261,7 @@ def generate(pin, rsa, pin_length, rsa_bits, words, output, password, as_json):
Examples:
stegasoo generate
stegasoo generate --words 5
stegasoo generate --rsa --rsa-bits 4096
stegasoo generate --rsa --rsa-bits 3072
stegasoo generate --rsa -o mykey.pem -p "secretpassword"
stegasoo generate --no-pin --rsa
"""

9
frontends/web/app.py
View File

@@ -253,6 +253,7 @@ from stegasoo.qr_utils import (
detect_and_crop_qr,
extract_key_from_qr,
generate_qr_code,
is_compressed,
)
# Initialize subprocess wrapper (worker script must be in same directory)
@@ -1209,8 +1210,8 @@ def encode_page():
rsa_key_from_qr = False
if rsa_key_pem:
# Webcam-scanned PEM key (v4.1.5) - may be compressed
if rsa_key_pem.startswith("STEGASOO-Z:"):
# Webcam-scanned PEM key (v4.1.5+) - may be compressed (zlib or zstd)
if is_compressed(rsa_key_pem):
rsa_key_pem = decompress_data(rsa_key_pem)
rsa_key_data = rsa_key_pem.encode("utf-8")
rsa_key_from_qr = True
@@ -1648,8 +1649,8 @@ def decode_page():
rsa_key_from_qr = False
if rsa_key_pem:
# Webcam-scanned PEM key (v4.1.5) - may be compressed
if rsa_key_pem.startswith("STEGASOO-Z:"):
# Webcam-scanned PEM key (v4.1.5+) - may be compressed (zlib or zstd)
if is_compressed(rsa_key_pem):
rsa_key_pem = decompress_data(rsa_key_pem)
rsa_key_data = rsa_key_pem.encode("utf-8")
rsa_key_from_qr = True

2
frontends/web/templates/about.html
View File

@@ -573,7 +573,7 @@
</tr>
<tr>
<td><i class="bi bi-shield me-2"></i>RSA keys</td>
<td><strong>2048, 3072, 4096 bit</strong></td>
<td><strong>2048, 3072 bit</strong></td>
</tr>
<tr>
<td><i class="bi bi-chat-quote me-2"></i>Passphrase</td>

10
frontends/web/templates/generate.html
View File

@@ -65,11 +65,7 @@
<select name="rsa_bits" class="form-select form-select-sm" id="rsaBitsSelect">
<option value="2048" selected>2048 bits (~128 bits entropy)</option>
<option value="3072">3072 bits (~128 bits entropy)</option>
<option value="4096">4096 bits (~128 bits entropy)</option>
</select>
<div class="form-text text-warning d-none" id="rsaQrWarning">
<i class="bi bi-exclamation-triangle me-1"></i>QR code unavailable for keys &gt;3072 bits
</div>
</div>
</div>
</div>
@@ -286,12 +282,6 @@
<i class="bi bi-shield-exclamation me-1"></i>
<strong>Security note:</strong> The QR code contains your unencrypted private key.
Only scan in a secure environment. Consider using the password-protected download instead.
{% if rsa_bits >= 4096 %}
<br><br>
<i class="bi bi-exclamation-triangle me-1"></i>
<strong>4096-bit keys</strong> produce very dense QR codes. If scanning fails,
use the PEM text or download options instead.
{% endif %}
</div>
</div>
</div>