# 使用X25519进行密钥协商


对应的算法规格请查看[密钥协商算法规格：X25519](crypto-key-agreement-overview.md#x25519)。


## 开发步骤

1. 调用[cryptoFramework.createAsyKeyGenerator](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreateasykeygenerator)、[AsyKeyGenerator.generateKeyPair](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#generatekeypair-1)、[AsyKeyGenerator.convertKey](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#convertkey-3)生成密钥算法为X25519的非对称密钥（KeyPair）。
   如何生成X25519非对称密钥，开发者可参考下文示例，并结合[非对称密钥生成和转换规格：X25519](crypto-asym-key-generation-conversion-spec.md#x25519)和[随机生成非对称密钥对](crypto-generate-asym-key-pair-randomly.md)理解，参考文档与当前示例可能存在入参差异，请在阅读时注意区分。

2. 调用[cryptoFramework.createKeyAgreement](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreatekeyagreement)，指定字符串参数'X25519'，创建密钥算法为X25519的密钥协议生成器（KeyAgreement）。

3. 调用[KeyAgreement.generateSecret](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#generatesecret-1)，基于传入的私钥（KeyPair.priKey）与公钥（KeyPair.pubKey）进行密钥协商，返回共享秘密。

- 以使用await方式，完成密钥协商为例：

  ```ts
  import { cryptoFramework } from '@kit.CryptoArchitectureKit';

  async function x25519Await() {
    // 假设此公私钥对数据为外部传入
    let pubKeyArray = new Uint8Array([48, 42, 48, 5, 6, 3, 43, 101, 110, 3, 33, 0, 36, 98, 216, 106, 74, 99, 179, 203, 81, 145, 147, 101, 139, 57, 74, 225, 119, 196, 207, 0, 50, 232, 93, 147, 188, 21, 225, 228, 54, 251, 230, 52]);
    let priKeyArray = new Uint8Array([48, 46, 2, 1, 0, 48, 5, 6, 3, 43, 101, 110, 4, 34, 4, 32, 112, 65, 156, 73, 65, 89, 183, 39, 119, 229, 110, 12, 192, 237, 186, 153, 21, 122, 28, 176, 248, 108, 22, 242, 239, 179, 106, 175, 85, 65, 214, 90]);
    let keyGen = cryptoFramework.createAsyKeyGenerator('X25519');
    // 外部传入的公私钥对A
    let keyPairA = await keyGen.convertKey({ data: pubKeyArray }, { data: priKeyArray });
    // 内部生成的公私钥对B
    let keyPairB = await keyGen.generateKeyPair();
    let keyAgreement = cryptoFramework.createKeyAgreement('X25519');
    // 使用A的公钥和B的私钥进行密钥协商
    let secret1 = await keyAgreement.generateSecret(keyPairB.priKey, keyPairA.pubKey);
    // 使用A的私钥和B的公钥进行密钥协商
    let secret2 = await keyAgreement.generateSecret(keyPairA.priKey, keyPairB.pubKey);
    // 两种协商的结果应当一致
    if (secret1.data.toString() == secret2.data.toString()) {
      console.info('x25519 success');
      console.info('x25519 output is ' + secret1.data);
    } else {
      console.error('x25519 result is not equal');
    }
  }
  ```

- 同步方法示例：

  ```ts
  import { cryptoFramework } from '@kit.CryptoArchitectureKit';

  function x25519Await() {
    // 假设此公私钥对数据为外部传入
    let pubKeyArray = new Uint8Array([48, 42, 48, 5, 6, 3, 43, 101, 110, 3, 33, 0, 36, 98, 216, 106, 74, 99, 179, 203, 81, 145, 147, 101, 139, 57, 74, 225, 119, 196, 207, 0, 50, 232, 93, 147, 188, 21, 225, 228, 54, 251, 230, 52]);
    let priKeyArray = new Uint8Array([48, 46, 2, 1, 0, 48, 5, 6, 3, 43, 101, 110, 4, 34, 4, 32, 112, 65, 156, 73, 65, 89, 183, 39, 119, 229, 110, 12, 192, 237, 186, 153, 21, 122, 28, 176, 248, 108, 22, 242, 239, 179, 106, 175, 85, 65, 214, 90]);
    let keyGen = cryptoFramework.createAsyKeyGenerator('X25519');
    // 外部传入的公私钥对A
    let keyPairA = keyGen.convertKeySync({ data: pubKeyArray }, { data: priKeyArray });
    // 内部生成的公私钥对B
    let keyPairB = keyGen.generateKeyPairSync();
    let keyAgreement = cryptoFramework.createKeyAgreement('X25519');
    // 使用A的公钥和B的私钥进行密钥协商
    let secret1 = keyAgreement.generateSecretSync(keyPairB.priKey, keyPairA.pubKey);
    // 使用A的私钥和B的公钥进行密钥协商
    let secret2 = keyAgreement.generateSecretSync(keyPairA.priKey, keyPairB.pubKey);
    // 两种协商的结果应当一致
    if (secret1.data.toString() == secret2.data.toString()) {
      console.info('x25519 success');
      console.info('x25519 output is ' + secret1.data);
    } else {
      console.error('x25519 result is not equal');
    }
  }
  ```