1# 使用ECC压缩/非压缩点格式转换
2
3支持将压缩/非压缩的点数据,转换为Point对象,用于密钥对象生成;也支持将Point对象转换为压缩/非压缩的点数据。
4ECC的算法规格请查看[非对称密钥生成和转换规格:ECC](crypto-asym-key-generation-conversion-spec.md#ecc)。
5通过传入字符串参数format,可指定需要获取的点数据格式。如果需要获取压缩格式,则指定format为:"COMPRESSED";需要获取非压缩格式,则指定format为:"UNCOMPRESSED"。
6
7
8## 指定非压缩点数据转换为压缩点数据
9
101. 指定Uint8Array类型的ECC非压缩点数据,调用[ECCKeyUtil.convertPoint](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#convertpoint12),构造[Point](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#point10)对象,用于生成点数据。
112. 调用[ECCKeyUtil.getEncodedPoint](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#getencodedpoint12),获取压缩点数据。
12
13```ts
14import { cryptoFramework } from '@kit.CryptoArchitectureKit';
15
16function eccPointUncompressedToCompressed() {
17  let pkData = new Uint8Array([4, 143, 39, 57, 249, 145, 50, 63, 222, 35, 70, 178, 121, 202, 154, 21, 146, 129, 75, 76, 63, 8, 195, 157, 111, 40, 217, 215, 148, 120, 224, 205, 82, 83, 92, 185, 21, 211, 184, 5, 19, 114, 33, 86, 85, 228, 123, 242, 206, 200, 98, 178, 184, 130, 35, 232, 45, 5, 202, 189, 11, 46, 163, 156, 152]);
18  let returnPoint = cryptoFramework.ECCKeyUtil.convertPoint('NID_brainpoolP256r1', pkData);
19  console.info('convertPoint success');
20  let returnData = cryptoFramework.ECCKeyUtil.getEncodedPoint('NID_brainpoolP256r1', returnPoint, 'COMPRESSED');
21  console.info('returnData: ' + returnData); // (因为y为偶数,所以压缩点数据的前缀是02)returnData: 2,143,39,57,249,145,50,63,222,35,70,178,121,202,154,21,146,129,75,76,63,8,195,157,111,40,217,215,148,120,224,205,82
22}
23```
24
25
26## 指定压缩点数据获取密钥对象
27
281. 指定Uint8Array类型的ECC压缩点数据,调用[ECCKeyUtil.convertPoint](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#convertpoint12),得到[Point](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#point10)对象,用于密钥对象生成。
292. 调用[ECCKeyUtil.genECCCommonParamsSpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#genecccommonparamsspec11),指定曲线名'NID_brainpoolP256r1',生成ECC的非对称公共密钥参数。
303. 构造[ECCPubKeySpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#eccpubkeyspec10)对象,用于指定ECC算法中公钥包含的参数。ECCPubKeySpec是AsyKeySpec的子类。需要通过参数algName指定算法'ECC';
31指定密钥参数类型[AsyKeySpecType.PUBLIC_KEY_SPEC](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#asykeyspectype10),参数pk指定为得到的point对象。
324. 通过得到的公钥参数,调用[createAsyKeyGeneratorBySpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#cryptoframeworkcreateasykeygeneratorbyspec10),创建非对称密钥生成器(AsyKeyGeneratorBySpec)。
335. 调用[AsyKeyGeneratorBySpec.generatePubKey](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#generatepubkey-1),得到指定的公钥。
346. 调用[ECCKeyUtil.getEncodedPoint](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#getencodedpoint12),得到非压缩点数据。
357. 调用[PubKey.getAsyKeySpec](../../reference/apis-crypto-architecture-kit/js-apis-cryptoFramework.md#getasykeyspec10),获取ECC算法中公钥pk的x坐标。
36
37```ts
38import { cryptoFramework } from '@kit.CryptoArchitectureKit';
39
40async function eccPointCompressedToPoint() {
41  let pkData = new Uint8Array([2, 143, 39, 57, 249, 145, 50, 63, 222, 35, 70, 178, 121, 202, 154, 21, 146, 129, 75, 76, 63, 8, 195, 157, 111, 40, 217, 215, 148, 120, 224, 205, 82]);
42  let returnPoint = cryptoFramework.ECCKeyUtil.convertPoint('NID_brainpoolP256r1', pkData);
43  console.info('convertPoint success');
44  let eccCommonParamsSpec = cryptoFramework.ECCKeyUtil.genECCCommonParamsSpec('NID_brainpoolP256r1');
45  let eccPubKeySpec: cryptoFramework.ECCPubKeySpec = {
46    algName: "ECC",
47    specType: cryptoFramework.AsyKeySpecType.PUBLIC_KEY_SPEC,
48    params: eccCommonParamsSpec,
49    pk: returnPoint
50  };
51  let generatorBySpec = cryptoFramework.createAsyKeyGeneratorBySpec(eccPubKeySpec);
52  let pubKey = await generatorBySpec.generatePubKey();
53  let returnData = cryptoFramework.ECCKeyUtil.getEncodedPoint('NID_brainpoolP256r1', returnPoint, 'UNCOMPRESSED');
54  console.info('returnData: ' + returnData); // 4,143,39,57,249,145,50,63,222,35,70,178,121,202,154,21,146,129,75,76,63,8,195,157,111,40,217,215,148,120,224,205,82,83,92,185,21,211,184,5,19,114,33,86,85,228,123,242,206,200,98,178,184,130,35,232,45,5,202,189,11,46,163,156,152
55  let eccPkX = pubKey.getAsyKeySpec(cryptoFramework.AsyKeySpecItem.ECC_PK_X_BN);
56  console.info('returnPoint x data: ' + returnPoint.x); // 64750044510792891439269945828433327517677381559622384455951527515863444933970
57  console.info('ECC_PK_X_BN:' + eccPkX); // 64750044510792891439269945828433327517677381559622384455951527515863444933970
58}
59```