sawtooth / bitcoin compact signature generation

sawtooth_signing.clj

(ns sawtooth-signing
  (:import org.bitcoinj.core.ECKey
           org.bitcoinj.core.DumpedPrivateKey
           org.bitcoinj.core.Sha256Hash
           org.bitcoinj.core.Utils
           org.bitcoinj.params.MainNetParams))

(def ^{:doc "generates an in-memory priv key representation from the .wif"}
  wif->key
  (let [MAINNET (MainNetParams/get)]
    (fn [s]
      (-> (DumpedPrivateKey/fromBase58 MAINNET s)
          (.getKey)))))

;; https://bitcoin.stackexchange.com/a/19539
(defn priv->pub
  "Returns the compressed format public key (65 bytes) from the uncompressed hex (130 bytes)"
  [^ECKey private-key]
  (let [uncompressed (.getPublicKeyAsHex private-key)]
    (str "03" (subs uncompressed 2 66))))

;; https://stackoverflow.com/q/34063694/1422711
(defn sign
  "sign a byte array and return a hex representation of the bitcoin 'compact signature'"
  [^ECKey pk ^bytes data]
  (let [h (Sha256Hash/of data)
        sig (.sign pk h)
        arr (byte-array 64)]
    (System/arraycopy (Utils/bigIntegerToBytes (.-r sig) 32) 0 arr 0 32)
    (System/arraycopy (Utils/bigIntegerToBytes (.-s sig) 32) 0 arr 32 32)

    (.encode Utils/HEX arr)))