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https://github.com/saymrwulf/swisspost-evoting-go-poc.git
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saymrwulf
bc43c3d3aa
The running cryptography now narrates itself. Each headline operation emits a
trace.Event carrying its LaTeX notation plus the actual runtime values, the
instant it executes:
- Ed25519 signature on every inter-party message (envelope.Seal)
- X25519 ECDH key agreement for confidential card delivery (NewSecureChannel)
- ElGamal ballot encryption E1 = (g^r, pk^r·m) with the real r (castBallot)
- Fiat-Shamir challenge e = H(...) mod q (Schnorr proof)
- Bayer-Groth verifiable shuffle C' = {ReEnc_pk(C_π(i))} with N (mix-net)
Ceremony phases set trace phase/party context so events are attributed to the
acting stakeholder and phase. Instrumentation is behind the enabled-check, so
normal runs pay nothing.
Test: a full traced ceremony captures 184 live events across all five headline
kinds, each with non-empty LaTeX and live values, correctly phase/party-tagged.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
70 lines
1.8 KiB
Go
70 lines
1.8 KiB
Go
package mixnet
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import (
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"fmt"
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"github.com/user/evote/pkg/elgamal"
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emath "github.com/user/evote/pkg/math"
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"github.com/user/evote/pkg/trace"
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)
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// VerifiableShuffle holds the result of a verifiable shuffle.
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type VerifiableShuffle struct {
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ShuffledCiphertexts *elgamal.CiphertextVector
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Argument ShuffleArgument
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}
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// GenVerifiableShuffle performs a shuffle and generates a proof.
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func GenVerifiableShuffle(
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C *elgamal.CiphertextVector,
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pk elgamal.PublicKey,
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group *emath.GqGroup,
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) VerifiableShuffle {
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// Determine matrix dimensions
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N := C.Size()
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_, n := GetMatrixDimensions(N)
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// Generate commitment key of size n
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ck := GenCommitmentKey(n, group)
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// Perform shuffle
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shuffle := GenShuffle(C, pk)
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// Generate shuffle argument
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arg := GenShuffleArgument(C, shuffle.Shuffled, shuffle.Perm, shuffle.Rho, pk, ck, group)
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trace.EmitFunc(func() trace.Event {
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return trace.Event{
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Kind: trace.KindShuffle,
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Caption: fmt.Sprintf("Bayer-Groth verifiable shuffle of %d ciphertexts", N),
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LaTeX: `\mathbf{C}' = \big\{\, \mathrm{ReEnc}_{pk}\!\big(C_{\pi(i)};\, \rho_i\big) \,\big\}_{i=1}^{\VAL{N}}, \qquad \pi \xleftarrow{\$} S_{\VAL{N}}`,
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ASCII: "C' = { ReEnc_pk(C_π(i); ρ_i) } for a secret permutation π",
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Values: map[string]string{
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"N": fmt.Sprintf("%d", N),
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"m": fmt.Sprintf("%d", N/n),
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"n": fmt.Sprintf("%d", n),
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},
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}
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})
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return VerifiableShuffle{
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ShuffledCiphertexts: shuffle.Shuffled,
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Argument: arg,
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}
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}
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// VerifyShuffle verifies a verifiable shuffle.
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func VerifyShuffle(
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C *elgamal.CiphertextVector,
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vs VerifiableShuffle,
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pk elgamal.PublicKey,
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group *emath.GqGroup,
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) bool {
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N := C.Size()
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_, n := GetMatrixDimensions(N)
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// Regenerate commitment key (deterministic from group)
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ck := GenCommitmentKey(n, group)
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return VerifyShuffleArgument(vs.Argument, C, vs.ShuffledCiphertexts, pk, ck, group)
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}
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