feat(rfid): add fdxb_encode — FDX-B (ISO 11784/11785) animal-microchip LF block generator#77
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…p LF block generator
The inverse of fdxb_decode (v0.464), extending the LF clone-generation set
(em4100_encode, ioprox_encode, noralsy_encode, viking_encode, jablotron_encode,
presco_encode) to the 134.2 kHz FDX-B animal/pet-microchip format. The decode
side shipped long ago but the synth side was the open half noted in the
gap-analysis LF-synth row; fdxb_encode produces the de-stuffed 10-byte ID+CRC
block an authorized operator would feed a transponder writer to clone a tag.
internal/fdxb.Encode is the exact inverse of Decode: the same LSB-first field
layout (38-bit national code at bit 0, 10-bit country at bit 38, the
data-block-status and animal-application flag bits at 48/49, reserved bits 50-63
zero) packed MSB-first into the 8-byte ID block, then the same Proxmark3 FDX-B
CRC-16 (CCITT poly 0x1021, init 0, output-reflected) appended LSB-first. The
on-air framing (11-bit preamble + the control '1' after every 8 bits) and the
24-bit vendor-specific extended block are out of scope, exactly as on the decode
side. Generation only — produces a block, transmits nothing and writes to no
device, so it is Low risk like the decoder.
Verification (the project's inverse-generator pattern): decode-of-encode
round-trips across six value sets — both of the decoder's real-tag anchors
(country 528 / national 140000795552 and country 999 / national 1500030037),
the 0/0 minimum, the 38-bit/10-bit maxima with both flags, and mid-range
values — each reproducing the national / country / flags with a valid CRC (the
shipped decoder is the independent oracle). Plus a published-vector anchor: the
identity bytes of the 528/140000795552 tag (national + country + flags, bytes
0..6) reproduce that real tag's ID block byte-for-byte as 05D94D19042100; the
real tag additionally carries a set reserved bit in byte 7 (bit 63, RFU range),
which the canonical encoder zeroes — asserted and documented. Out-of-range
national (>38 bits) and country (>10 bits, negative) are rejected.
Wired: internal/fdxb/{encode.go,encode_test.go}, internal/tools/fdxb_encode.go,
risk.go classification (Low, consistency test green), registry_size_test.go
680 -> 681 (count + comment), and the gap-analysis LF-synth row. gofmt /
go vet / golangci-lint (0 issues) / go test -race (fdxb, risk, tools) green.
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What
Adds
fdxb_encode, the inverse offdxb_decode(v0.464), extending the LF clone-generation set (em4100_encode,ioprox_encode,noralsy_encode,viking_encode,jablotron_encode,presco_encode) to the 134.2 kHz FDX-B animal/pet-microchip format. The decode side shipped long ago; the synth side was the open half noted in the gap-analysis LF-synth row. It produces the de-stuffed 10-byte ID+CRC block an authorized operator would feed a transponder writer to clone a tag.How
internal/fdxb.Encodeis the exact inverse ofDecode: the same LSB-first field layout (38-bit national @ bit 0, 10-bit country @ bit 38, data-block + animal flag bits @ 48/49, reserved 50-63 zero) packed MSB-first into the 8-byte ID block, then the same Proxmark3 FDX-B CRC-16 (CCITT0x1021, init 0, output-reflected) appended LSB-first. On-air framing and the 24-bit vendor extended block are out of scope, exactly as on decode. Generation only → Low risk.Verification (inverse-generator pattern)
decode∘encode round-trip across six value sets — both of the decoder's real-tag anchors (528/140000795552, 999/1500030037), the 0/0 minimum, the 38-bit/10-bit maxima + both flags, and mid-range — each reproducing national/country/flags with a valid CRC (the shipped decoder is the independent oracle).
published-vector anchor: the identity bytes of the 528/140000795552 tag (bytes 0..6) reproduce that real tag's ID block byte-for-byte as
05D94D19042100. The real tag also carries a set reserved bit in byte 7 (bit 63, RFU range), which the canonical encoder zeroes — asserted and documented.out-of-range national (>38 bits) / country (>10 bits, negative) rejected.
gofmt/go vetclean ·golangci-lint run ./...→ 0 issues ·go test -race ./internal/fdxb/ ./internal/risk/ ./internal/tools/→okregistry 680→681, risk-consistency + gated-set tests green; multi-param panic guard auto-covers it.
Wired
internal/fdxb/{encode.go,encode_test.go},internal/tools/fdxb_encode.go,risk.go(Low),registry_size_test.go(count + comment), gap-analysis LF-synth row.