类型错误：无法读取未定义的属性“elGamal”

如何解决类型错误：无法读取未定义的属性“elGamal”

我正在运行以下代码片段，但出现错误TypeError：无法读取未定义的属性“elGamal”

    var sjcl = require("sjcl");
    var keys = sjcl.ecc.elGamal.publicKey(); //choose a stronger/weaker curve

    var pubkem = keys.pub.kem(); //KEM is Key Encapsulation Mechanism
    var pubkey = pubkem.key;
    var seckey = keys.sec.unkem(pubkem.tag); //tag is used to derive the secret (private) key

    var plain = "Hello World!";
    var cipher = sjcl.encrypt(pubkey,plain); //defaults to AES
    var result = sjcl.decrypt(seckey,cipher);

    console.log(plain === result); //true