blog: flash fse
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content/blog/flash-filesystem-encryption/diagram.py
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content/blog/flash-filesystem-encryption/diagram.py
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#!/usr/bin/python3
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"""
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GNU AGPL v3, CopyLeft 2025 Pascal Engélibert [(why copyleft?)](https://txmn.tk/blog/why-copyleft/)
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This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, version 3 of the License.
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This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License along with this program. If not, see https://www.gnu.org/licenses/.
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"""
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import math
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ARGS = {
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"BLACK": "#000",
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"WHITE": "#ddd",
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}
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SVG = """\
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<svg version="1.1" xmlns="http://www.w3.org/2000/svg" width="{w}" height="{h}" viewBox="0 0 {w} {h}">
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<!-- Generated by https://txmn.tk/blog/flash-filesystem-encryption/diagram.py -->
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<!-- Image released under license CC0 (public domain) -->
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<title>{title}</title>
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<style>
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text.t {{
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color: {BLACK};
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fill: {BLACK};
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text-anchor: middle;
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dominant-baseline: central;
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font-size: 16px;
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font-family: "Libertinus Sans";
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}}
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circle, line, rect, path.s {{
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stroke: {BLACK};
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stroke-width: 2px;
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fill: none;
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}}
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path.f {{
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stroke: none;
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fill: {BLACK};
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}}
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@media (prefers-color-scheme: dark) {{
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text.t {{
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color: {WHITE};
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fill: {WHITE};
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}}
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circle, line, rect, path.s {{
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stroke: {WHITE};
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}}
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path.f {{
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fill: {WHITE};
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}}
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}}
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</style>
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{body}
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</svg>
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"""
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class Block:
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def __init__(self, svg, x, y, r):
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self.svg = svg
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self.x = x
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self.y = y
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self.r = r
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def to(self, block):
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if self.x == block.x:
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if self.y > block.y:
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self.svg.t += arrow(self.x, self.y-self.r, block.x, block.y+block.r)
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else:
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self.svg.t += arrow(self.x, self.y+self.r, block.x, block.y-block.r)
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elif self.y == block.y:
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if self.x > block.x:
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self.svg.t += arrow(self.x-self.r, self.y, block.x+block.r, block.y)
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else:
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self.svg.t += arrow(self.x+self.r, self.y, block.x-block.r, block.y)
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XOR_R = 8
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ENCRYPT_SIZE = 32
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class Svg:
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def __init__(self):
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self.t = ""
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def xor(self, x, y):
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xl = x-XOR_R
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xr = x+XOR_R
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yt = y-XOR_R
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yb = y+XOR_R
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self.t += f"""\
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<circle r="{XOR_R}" cx="{x}" cy="{y}"/>
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<line x1="{xl}" y1="{y}" x2="{xr}" y2="{y}"/>
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<line x1="{x}" y1="{yt}" x2="{x}" y2="{yb}"/>
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"""
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return Block(self, x, y, XOR_R)
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def encrypt(self, x, y):
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xl = x-ENCRYPT_SIZE//2
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yt = y-ENCRYPT_SIZE//2
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self.t += f"""\
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<rect x="{xl}" y="{yt}" width="{ENCRYPT_SIZE}" height="{ENCRYPT_SIZE}"/>
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<text class="t" x="{x}" y="{y}">E</text>
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"""
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return Block(self, x, y, ENCRYPT_SIZE//2)
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def text(self, x, y, t):
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self.t += f"""\
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<text class="t" x="{x}" y="{y}">{t}</text>
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"""
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return Block(self, x, y, 12)
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def square(self, x, y, t):
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xl = x-ENCRYPT_SIZE//2
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yt = y-ENCRYPT_SIZE//2
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self.t += f"""\
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<rect x="{xl}" y="{yt}" width="{ENCRYPT_SIZE}" height="{ENCRYPT_SIZE}"/>
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<text class="t" x="{x}" y="{y}">{t}</text>
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"""
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return Block(self, x, y, ENCRYPT_SIZE//2)
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ARROW_TIP_START = 8
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ARROW_TIP_BACK = 12
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ARROW_TIP_R = 6
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ARROW_TIP = [
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(-ARROW_TIP_START, 0),
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(-ARROW_TIP_BACK, ARROW_TIP_R),
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(0, 0),
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(-ARROW_TIP_BACK, -ARROW_TIP_R),
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(-ARROW_TIP_START, 0),
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]
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def arrow(x1, y1, x2, y2):
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angle = math.degrees(math.atan2(y2-y1, x2-x1))
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# Stop the line before the end to prevent it from passing through the tip
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length = math.sqrt((x2-x1)**2+(y2-y1)**2)
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xend = x2 - (x2-x1)/length*ARROW_TIP_START
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yend = y2 - (y2-y1)/length*ARROW_TIP_START
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path = ""
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px = 0
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py = 0
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for p in ARROW_TIP:
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path += "l{} {}".format(p[0]-px, p[1]-py)
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px = p[0]
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py = p[1]
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return f"""\
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<line x1="{x1}" y1="{y1}" x2="{xend}" y2="{yend}"/>
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<path class="f" transform="translate({x2},{y2}) rotate({angle})" d="M0 0{path}z"/>
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"""
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def arrow_path(points):
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x1 = points[-2][0]
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y1 = points[-2][1]
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x2 = points[-1][0]
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y2 = points[-1][1]
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angle = math.degrees(math.atan2(y2-y1, x2-x1))
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# Stop the line before the end to prevent it from passing through the tip
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length = math.sqrt((x2-x1)**2+(y2-y1)**2)
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xend = x2 - (x2-x1)/length*ARROW_TIP_START
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yend = y2 - (y2-y1)/length*ARROW_TIP_START
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points[-1] = (xend, yend)
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path_arrow = ""
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px = 0
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py = 0
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for p in ARROW_TIP:
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path_arrow += "l{} {}".format(p[0]-px, p[1]-py)
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px = p[0]
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py = p[1]
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path_line = "M" + "L".join(["{} {}".format(p[0], p[1]) for p in points])
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return f"""\
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<path class="s" d="{path_line}"/>
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<path class="f" transform="translate({x2},{y2}) rotate({angle})" d="M0 0{path_arrow}z"/>
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"""
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def ecb():
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s = Svg()
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for i in range(3):
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P = s.text(96*i+64, 16, "P")
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K = s.text(96*i+16, 64, "K")
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E = s.encrypt(96*i+64, 64)
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C = s.text(96*i+64, 112, "C")
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P.to(E)
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K.to(E)
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E.to(C)
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return SVG.format(body=s.t, title="ECB", w=288, h=128, **ARGS)
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def ctr():
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s = Svg()
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for i in range(3):
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S = s.text(96*i+64, 16, f"N||{i}")
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K = s.text(96*i+16, 64, "K")
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E = s.encrypt(96*i+64, 64)
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P = s.text(96*i+16, 112, "P")
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X = s.xor(96*i+64, 112)
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C = s.text(96*i+64, 152, "C")
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S.to(E)
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K.to(E)
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E.to(X)
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P.to(X)
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X.to(C)
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return SVG.format(body=s.t, title="CTR", w=288, h=172, **ARGS)
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def cbc():
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s = Svg()
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for i in range(3):
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P = s.text(96*i+64, 16, "P")
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X = s.xor(96*i+64, 56)
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K = s.text(96*i+16, 96, "K")
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E = s.encrypt(96*i+64, 96)
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C = s.text(96*i+64, 144, "C")
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P.to(X)
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X.to(E)
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K.to(E)
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E.to(C)
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if i == 0:
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IV = s.text(96*i+16, 56, "IV")
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IV.to(X)
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s.t += arrow_path([(96*i+72,144), (96*i+96,144), (96*i+96,56), (96*(1+i)+56,56)])
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s.text(356, 56, "···")
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return SVG.format(body=s.t, title="CBC", w=372, h=172, **ARGS)
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def xts():
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s = Svg()
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P = s.text(224, 16, "P")
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X1 = s.xor(224, 56)
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E1 = s.encrypt(224, 96)
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X2 = s.xor(224, 144)
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C = s.text(224, 180, "C")
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K1 = s.text(176, 96, 'K<tspan dy="6">1</tspan>')
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I = s.text(64, 16, "i")
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E2 = s.encrypt(64, 96)
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K2 = s.text(16, 96, 'K<tspan dy="6">2</tspan>')
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J = s.text(128, 16, "j")
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A = s.square(128, 96, '×α <tspan dy="-8">j</tspan>')
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P.to(X1)
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X1.to(E1)
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K1.to(E1)
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I.to(E2)
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K2.to(E2)
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E1.to(X2)
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X2.to(C)
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E2.to(A)
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J.to(A)
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s.t += arrow_path([(144,96), (160,96), (160,56), (216,56)])
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s.t += arrow_path([(144,96), (160,96), (160,144), (216,144)])
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return SVG.format(body=s.t, title="XTS", w=372, h=192, **ARGS)
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def save(name, data):
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f = open(f"{name}.svg", "w")
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f.write(data)
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f.close()
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if __name__ == "__main__":
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save("ecb", ecb())
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save("ctr", ctr())
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save("cbc", cbc())
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save("xts", xts())
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