From c1decadb590c4d79d92bcc4df7772119a5c91244 Mon Sep 17 00:00:00 2001
From: Gab Virebent <gabriel1@virebent.art>
Date: Sat, 22 Aug 2026 20:36:56 +0200
Subject: Initial Aegis Usenet client release

---
 internal/identity/vface.go | 94 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 internal/identity/vface.go

(limited to 'internal/identity/vface.go')

diff --git a/internal/identity/vface.go b/internal/identity/vface.go
new file mode 100644
index 0000000..a5dcef5
--- /dev/null
+++ b/internal/identity/vface.go
@@ -0,0 +1,94 @@
+package identity
+
+import (
+	"crypto/sha256"
+	"encoding/base64"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"image"
+	"strings"
+
+	"aegis/internal/cryptokit"
+)
+
+const VFaceVerificationURL = "https://identicons.virebent.art"
+
+// VFace is the deterministic public profile derived from the three identity
+// fields username, email and Ed25519 public key. The private key is never part
+// of this structure.
+type VFace struct {
+	Username        string
+	Email           string
+	PublicKey       string
+	Input           string
+	IdentityHash    string
+	PNGHash         string
+	FaceBase64      string
+	VerificationURL string
+}
+
+// GenerateVFace creates the optional 48x48 transparent PNG used by Face and
+// the profile preview. The seed is exactly username|email|public-key, matching
+// the VFace implementation used by M2Usenet and N2Usenet.
+func GenerateVFace(username, email, publicKey string) (VFace, error) {
+	username = strings.TrimSpace(username)
+	email = strings.TrimSpace(email)
+	if username == "" || email == "" {
+		return VFace{}, errors.New("VFace requires a username and email address")
+	}
+	if strings.ContainsAny(username+email, "\r\n|") {
+		return VFace{}, errors.New("VFace identity fields contain forbidden characters")
+	}
+	canonicalKey, err := cryptokit.CanonicalEd25519PublicKey(publicKey)
+	if err != nil {
+		return VFace{}, fmt.Errorf("canonicalize VFace public key: %w", err)
+	}
+	input := username + "|" + email + "|" + canonicalKey
+	faceBase64, err := generateFace(input, 48)
+	if err != nil {
+		return VFace{}, fmt.Errorf("generate VFace identicon: %w", err)
+	}
+	pngBytes, err := base64.StdEncoding.DecodeString(faceBase64)
+	if err != nil {
+		return VFace{}, fmt.Errorf("decode VFace PNG: %w", err)
+	}
+	if _, err := pngImage(pngBytes, 48); err != nil {
+		return VFace{}, err
+	}
+	identityDigest := sha256.Sum256([]byte(input))
+	pngDigest := sha256.Sum256(pngBytes)
+	return VFace{
+		Username:        username,
+		Email:           email,
+		PublicKey:       canonicalKey,
+		Input:           input,
+		IdentityHash:    hex.EncodeToString(identityDigest[:]),
+		PNGHash:         hex.EncodeToString(pngDigest[:]),
+		FaceBase64:      faceBase64,
+		VerificationURL: VFaceVerificationURL,
+	}, nil
+}
+
+// Headers returns the interoperable VFace headers for an article or email.
+// The Face value is folded according to the existing identicon convention.
+func (v VFace) Headers() []string {
+	return []string{
+		FormatFaceHeader(v.FaceBase64),
+		"X-VFace-Version: 1",
+		"X-Ed25519-Pub: " + v.PublicKey,
+		"Identity-Hash: " + v.IdentityHash,
+		"X-VFace-Hash: sha256:" + v.IdentityHash,
+		"X-VFace-PNG-SHA256: " + v.PNGHash,
+		"X-VFace-Verify: " + v.VerificationURL,
+	}
+}
+
+// DecodeFacePNG decodes a generated VFace image for a GUI preview.
+func DecodeFacePNG(value string) (image.Image, error) {
+	data, err := base64.StdEncoding.DecodeString(strings.TrimSpace(value))
+	if err != nil {
+		return nil, fmt.Errorf("decode Face base64: %w", err)
+	}
+	return pngImage(data, 48)
+}
-- 
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