question: public byte [ ] sign ( byte [ ] hash ) { ECDSASigner signer = new ECDSASigner ( new HMacDSAKCalculator ( new SHA256Digest ( ) ) ) ; signer . init ( true , new ECPrivateKeyParameters ( priv , domain ) ) ; BigInteger [ ] signature = signer . generateSignature ( hash ) ; ByteArrayOutputStream baos = new ByteArrayOutputStream ( ) ; try { DERSequenceGenerator seq = new DERSequenceGenerator ( baos ) ; seq . addObject ( new ASN1Integer ( signature [ 0 ] ) ) ; seq . addObject ( new ASN1Integer ( toCanonicalS ( signature [ 1 ] ) ) ) ; seq . close ( ) ; return baos . toByteArray ( ) ; } catch ( IOException e ) { } return null ; }
target:  Sign a digest with this key.