Add the five-part learn/ folder (overview, concepts, architecture,
implementation, challenges) grounded in docs/research, with the
QR-from-ISO/IEC-18004 Reed-Solomon injection as the showpiece and crypha's
real capacities cited from the binary. Update the root README row from a
Python synopsis to the built Go project with Source Code and Docs links,
matching the nadezhda row.
Guided hide/reveal/capacity wizard in internal/tui as a pure view over internal/engine (no carrier logic): HCL gradient engine, live capacity meter, embed animation, and a secure-options form. Bare crypha on a TTY launches it; piped or --help prints help. Adds engine.Overhead and engine.EnvelopeSize for exact payload-fit preflight (flate pass only, no KDF).
Reimplements the QR internals needed for the covert channel from
ISO/IEC 18004: the function-module map, format-info parse, data mask,
zigzag placement, and error-correction block de-interleave, plus a
from-scratch Reed-Solomon decoder over GF(2^8) (syndromes, Berlekamp-
Massey, Chien search, and a Vandermonde magnitude solve). skip2 generates
the clean symbol; crypha introspects it and reuses none of its internals.
The payload is hidden as up to floor(t/2) correctable codeword errors per
block in the data region, leaving the error-correction codewords intact,
so any scanner's Reed-Solomon decoder self-heals to the cover and never
sees it. Reveal reads the module grid, RS-decodes each block itself, and
diffs the corrected data against the stego to recover the payload. EC
level is fixed at H; versions 1-10 auto-select by cover and payload size.
Capacity is tens of bytes, so an encrypted envelope (which exceeds it) is
rejected cleanly.
Differentially tested: the extracted codewords match skip2 as valid RS
codewords across all supported versions, and every stego still scans back
to the cover via gozxing at the full injection budget. skip2 is a runtime
dependency (the generator); gozxing is test-only. No toolchain bump; the
go directive stays 1.25.0.
M4 audio: 16-bit PCM WAV LSB carrier. Cover input is WAV or FLAC
(FLAC decoded via the mewkiz decoder); output is always 16-bit PCM
WAV. Native FLAC output is deferred. uint32 length-prefix framing
with overflow-safe bounds; in-memory WriteSeeker so the WAV encoder
can seek back and patch chunk sizes through the io.Writer interface.
M5 pdf: three techniques behind one carrier. Attachment (default,
pdfcpu embedded-file, lossless), metadata (base64url payload chunked
across custom Info-dict keys), and append-after-EOF (raw trailing
bytes, O(1) end-seek). Reveal auto-tries all three; technique
selection is exposed via New(Technique). The package disables the
pdfcpu config directory for hermeticity.
Both carriers self-register and are blank-imported in carrier/all.
No toolchain bump (go directive stays 1.25.0).
M2 image carrier: LSB embedding in PNG and 24-bit BMP covers via the
mandatory NRGBA conversion (avoids the premultiply LSB-corruption trap on
both encode paths), RGB-only with alpha untouched, uint32 length prefix,
paletted/16-bit/JPEG rejection, Capacity and Sniff, self-registering.
M3 text carrier: encrypted payload hidden as zero-width Unicode
(U+200B/U+2060) appended after cover text, magic + length framing that
survives incidental zero-width in the cover and NFC/NFD/NFKC/NFKD
normalization. Frame extraction consumes exactly to the end of the
carrier-bit stream so nested stego reveals the last-hidden layer.
New internal/carrier/all sentinel blank-imports carriers into the
registry. Adds golang.org/x/image/bmp and (test-only) golang.org/x/text.
CarterPerez-dev