# 使用SM2密文格式转换


当前支持的SM2密文格式为国密标准的ASN.1格式，其中各参数组合顺序为C1C3C2，具体参数含义请参考[转换SM2密文格式](crypto-asym-encrypt-decrypt-spec.md#转换sm2密文格式)。

开发者可指定SM2密文的参数，将其转换成符合国密标准的ASN.1格式密文。反之，也可以从国密标准的ASN.1格式密文中取出具体的SM2密文参数，便于开发者自行组合成其他格式的SM2密文。


**指定密文参数，生成标准ASN.1密文**


1. 构造[SM2CipherTextSpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#sm2ciphertextspec12)对象，用于指定SM2密文参数。如果开发者使用的不是国密标准的ASN.1格式密文，需自行提取所需要的参数。

2. 调用[genCipherTextBySpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#genciphertextbyspec12)，将SM2CipherTextSpec对象传入，生成符合国密标准的ASN.1格式的SM2密文。

3. 生成的密文可直接使用cryptoFramework进行SM2解密。

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

function testGenCipherTextBySpec() {
  let spec : cryptoFramework.SM2CipherTextSpec = {
      xCoordinate: BigInt('20625015362595980457695435345498579729138244358573902431560627260141789922999'),
      yCoordinate: BigInt('48563164792857017065725892921053777369510340820930241057309844352421738767712'),
      cipherTextData: new Uint8Array([100, 227, 78, 195, 249, 179, 43, 70, 242, 69, 169, 10, 65, 123]),
      hashData: new Uint8Array([87, 167, 167, 247, 88, 146, 203, 234, 83, 126, 117, 129, 52, 142, 82, 54, 152, 226, 201, 111, 143, 115, 169, 125, 128, 42, 157, 31, 114, 198, 109, 244]),
  }
  // 此处的data可直接使用cryptoFramework进行SM2解密
  let data = cryptoFramework.SM2CryptoUtil.genCipherTextBySpec(spec, 'C1C3C2');
  console.info('genCipherTextBySpec success');
}
```


**从标准ASN.1密文中，获取密文参数**


1. 准备符合国密标准的ASN.1格式的SM2密文。

2. 调用[getCipherTextSpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#genciphertextbyspec12)，从标准密文中，获取具体的SM2密文参数。

3. 根据业务需要，自行拼接SM2密文参数，形成其他格式的SM2密文。

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

function testGetCipherTextSpec() {
  let cipherTextArray = new Uint8Array([48, 118, 2, 32, 45, 153, 88, 82, 104, 221, 226, 43, 174, 21, 122, 248, 5, 232, 105, 41, 92, 95, 102, 224, 216, 149, 85, 236, 110, 6, 64, 188, 149, 70, 70, 183, 2, 32, 107, 93, 198, 247, 119, 18, 40, 110, 90, 156, 193, 158, 205, 113, 170, 128, 146, 109, 75, 17, 181, 109, 110, 91, 149, 5, 110, 233, 209, 78, 229, 96, 4, 32, 87, 167, 167, 247, 88, 146, 203, 234, 83, 126, 117, 129, 52, 142, 82, 54, 152, 226, 201, 111, 143, 115, 169, 125, 128, 42, 157, 31, 114, 198, 109, 244, 4, 14, 100, 227, 78, 195, 249, 179, 43, 70, 242, 69, 169, 10, 65, 123]);
  let cipherText : cryptoFramework.DataBlob = {data : cipherTextArray};
  let spec : cryptoFramework.SM2CipherTextSpec = cryptoFramework.SM2CryptoUtil.getCipherTextSpec(cipherText, 'C1C3C2');
  console.info('getCipherTextSpec success');
}
```