Rework API

src/private-box.ts

@@ -0,0 +1,59 @@
+import logger from 'log'
+import SecretBox from './secret-box'
+import {DHusage, ecdh} from './kdf'
+import {pubkey_fromString, pubkey_toString, Usage} from './misc'
+import * as consts from './const'
+
+const log = logger('crypto:private-box')
+
+export default class PrivateBox {
+  private constructor(
+    private readonly pubkey: CryptoKey,
+    private readonly box: SecretBox
+  ) {}
+
+  public static gen(extractable: boolean = true): Promise<CryptoKeyPair> {
+    log.trace('generate keypair')
+    log.trace('Extractable :', extractable)
+    try {
+      return crypto.subtle.generateKey(consts.ECDH, extractable, ['deriveKey']) as Promise<CryptoKeyPair>
+    } catch(e) {
+      log.warn("Failed to generate a key")
+      log.debug("Error :", e)
+      throw e
+    }
+  }
+
+  public static async encrypt(data: Uint8Array, pubkey: CryptoKey): Promise<PrivateBox> {
+    log.trace('encrypt')
+    const tmp_pair = await PrivateBox.gen(false)
+    const key = await ecdh(tmp_pair.privateKey, pubkey, DHusage.box)
+    const box = await SecretBox.encrypt(data, key)
+    return new this(tmp_pair.publicKey, box)
+  }
+  public async decrypt(privkey: CryptoKey): Promise<Uint8Array | null> {
+    log.trace('decrypt')
+    const key = await ecdh(privkey, this.pubkey, DHusage.box)
+    return this.box.decrypt(key)
+  }
+
+  public async toString(): Promise<string> {
+    log.trace('toString')
+    const pubkey = await pubkey_toString(this.pubkey)
+    const box = this.box.toString()
+    return `${pubkey}.${box}`
+  }
+  public static async fromString(data: string): Promise<PrivateBox | null> {
+    log.trace('fromString')
+
+    const parts = data.split('.')
+    if (parts.length < 2) return null
+
+    const pubkey = await pubkey_fromString(parts[0], Usage.ecdh)
+    if (pubkey === null) return null
+    const box = SecretBox.fromString(parts.slice(1).join("."))
+    if (box === null) return null
+
+    return new PrivateBox(pubkey, box)
+  }
+}