diff --git a/index.js b/index.js
index e427d08..b3926a6 100644
--- a/index.js
+++ b/index.js
@@ -176,23 +176,24 @@ class TICrypto {
    * @return {String}
    * @memberof TICrypto
    */
-  static async encrypt(data, { keytype = 'pwd', key, input, output, cipher } = {}) {
+  static async encrypt(data, { tool, keytype = 'pwd', key, input, output, cipher } = {}) {
     if (tool === 'eccrypto') {
       // data 应当是 utf8 的字符串。key 必须是 pubkey
       // eccrypto 能用 Uint8Array 和 Buffer
       // eccrypto-js 只能用 Buffer
       // 在浏览器里 https://github.com/bitchan/eccrypto 库报错，即使用了 Uint8Array: Failed to execute 'encrypt' on 'SubtleCrypto': The provided value is not of type '(ArrayBuffer or ArrayBufferView)'
       let cipherobject = await eccrypto.encrypt(Buffer.from(this.hex2buf(key)), data) // 对 eccrypto 库，使用
-      return cipherobject // 返回一个复杂的结构。对同样的key和data，每次返回的结果不一样
+      return cipherobject // 返回一个复杂的结构 {iv:Buffer, ciphertext:Buffer, ...}。对同样的key和data，每次返回的结果不一样
     } else if (keytype === 'pwd') {
+      // 对称加密
       if (typeof key === 'string') {
         let inputEncoding = my.INPUT_LIST.indexOf(input) >= 0 ? input : my.INPUT // 'utf8' by default, 'ascii', 'latin1' for string  or ignored for Buffer/TypedArray/DataView
         let outputEncoding = output === 'buf' ? undefined : my.OUTPUT_LIST.indexOf(output) >= 0 ? output : my.OUTPUT // 'latin1', 'base64', 'hex' by default or 'buf' to Buffer explicitly
         const iv = crypto.randomBytes(16)
-        let ciph = crypto.createCipheriv(my.CIPHER_LIST.indexOf(cipher) >= 0 ? cipher : my.CIPHER, this.hex2buf(this.hash(key)), iv)
+        let encryptor = crypto.createCipheriv(my.CIPHER_LIST.indexOf(cipher) >= 0 ? cipher : my.CIPHER, this.hex2buf(this.hash(key)), iv) // cipher 和 key 的长度必须相同，例如 cipher 是 ***-192，那么 key 就必须是 192/8=24 字节 = 48 hex 的。
         if (typeof data !== 'string' && !(data instanceof Buffer) && !(data instanceof DataView)) data = JSON.stringify(data)
-        let ciphertext = ciph.update(data, inputEncoding, outputEncoding)
-        ciphertext += ciph.final(outputEncoding) // 但是 Buffer + Buffer 还是会变成string
+        let ciphertext = encryptor.update(data, inputEncoding, outputEncoding)
+        ciphertext += encryptor.final(outputEncoding) // 但是 Buffer + Buffer 还是会变成string
         return { iv: iv.toString('hex'), ciphertext }
       }
     } else if (keytype === 'seckey') {
@@ -215,7 +216,7 @@ class TICrypto {
    * @return {String}
    * @memberof TICrypto
    */
-  static async decrypt(data = {}, { keytype = 'pwd', key, input, output, cipher } = {}) {
+  static async decrypt(data = {}, { tool, keytype = 'pwd', key, input, output, cipher } = {}) {
     // data 应当是 encrypt 输出的数据类型
     if (tool === 'eccrypto') {
       try {
@@ -228,16 +229,17 @@ class TICrypto {
         return null
       }
     } else if (keytype === 'pwd') {
+      // 对称解密
       if ((typeof data.ciphertext === 'string' || data.ciphertext instanceof Buffer) && typeof key === 'string') {
         let inputEncoding = my.OUTPUT_LIST.indexOf(input) >= 0 ? input : my.OUTPUT // input (=output of encrypt) could be 'latin1', 'base64', 'hex' by default for string or ignored for Buffer
         let outputEncoding = output === 'buf' ? undefined : my.INPUT_LIST.indexOf(output) >= 0 ? output : my.INPUT // output (=input of encrypt) could be 'latin1', 'ascii', 'utf8' by default or  'buf' to Buffer explicitly
-        let decipher = crypto.createDecipheriv(
+        let decryptor = crypto.createDecipheriv(
           my.CIPHER_LIST.indexOf(cipher) >= 0 ? cipher : my.CIPHER,
           this.hex2buf(this.hash(key)),
           Buffer.from(data.iv, 'hex')
         )
-        let decrypted = decipher.update(data.ciphertext, inputEncoding, outputEncoding)
-        decrypted += decipher.final(outputEncoding) // 但是 Buffer + Buffer 还是会变成string
+        let decrypted = decryptor.update(data.ciphertext, inputEncoding, outputEncoding)
+        decrypted += decryptor.final(outputEncoding) // 但是 Buffer + Buffer 还是会变成string
         // 如果用户输入错误密码，deciper也能解密，无法自动判断是否正确结果。可在返回后人工判断。
         return decrypted
       }