Avoid repeat decoding

Author: emmansun

src/sm2.js

@@ -28,7 +28,7 @@ const SM2_CURVE_PARAM_B = '28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCB
 const SM2_CURVE_PARAM_N = 'FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123'
 const SM2_CURVE_PARAM_GX = '32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7'
 const SM2_CURVE_PARAM_GY = 'BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0'
-const SM2_CURVE_PARAMS_FOR_ZA = 'FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E9332C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0'
+const SM2_CURVE_PARAMS_FOR_ZA = util.hexToUint8Array('FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E9332C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0')
 
 const CIPHERTEXT_ENCODING_PLAIN = 0
 const CIPHERTEXT_ENCODING_ASN1 = 1
@@ -317,7 +317,7 @@ function adaptSM2 (ecdsa) {
       const md = new MessageDigest()
       md.update(Uint8Array.from([0xff & (entla >>> 8), 0xff & entla]))
       md.update(uid)
-      md.update(util.hexToUint8Array(SM2_CURVE_PARAMS_FOR_ZA)) // a||b||gx||gy
+      md.update(SM2_CURVE_PARAMS_FOR_ZA) // a||b||gx||gy
       let Q
       if (this.pubKeyHex) {
         Q = rs.ECPointFp.decodeFromHex(this.ecparams.curve, this.pubKeyHex)