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我们需要验证来自服务器的哈希值。Android 部分正在运行。在 iOS 端，我们使用 CryptoKit 来生成哈希值。作为参数传递“jsonString”，需要从中生成哈希键和需要匹配的“hasValue”。虽然这两个函数使用相同的算法，但结果总是不同的。

让摘要 = SHA512.hash（数据：jsonStringWithSaltBytes）

让 hasBytes = digest.bytes

在 computeHas 函数中，当我们尝试获取let hasBytes = digest.bytesSHA512.hash 字节转换后它总是给出不同的 HashBytes。

import CryptoKit

extension Digest {
    var bytes: [UInt8] { Array(makeIterator()) }
    var data: Data { Data(bytes) }
}

func generateHasKey(jsonString: String, hasValue: String) -> Bool {
    let data = Data(base64Encoded: hasValue)
    let hashWithSaltByte: [UInt8] = Array(data!)
    let hashSizeByts: Int = 512 / 8
    if hashWithSaltByte.count < hashSizeByts {
        return false
    }
    var saltBytesArr: [UInt8] = Array(repeating: 0, count: (hasWithSaltByte.count - hashSizeInByts))
    for index in 0..<saltBytes.count {
        saltBytesArr[index] = hasWithSaltByte[hashSizeInByts + index]
    }
    let expectedHasString = computeHas(jsonString: jsonString, saltBytes: saltBytesArr)
    if expectedHashString == hasValue {
        print("Hash value match..")
        return true
    }else {
        print("Hash value did not match..")
        return false
    }

}

func computeHash(jsonString: String, saltBytes: [UInt8]) -> String {
    let saltBytes = saltBytes
    let jsonStringBytes: [UInt8] = Array(jsonString.utf8)
    var jsonStringWithSaltBytes: [UInt8] =  Array(repeating: 0, count: (jsonStringBytes.count + saltBytes.count))
    for index in 0..<jsonStringBytes.count {
        jsonStringWithSaltBytes[index] = jsonStringBytes[index]
    }
    for index in 0..<saltBytes.count {
        jsonStringWithSaltBytes[jsonStringBytes.count + index] = saltBytes[index]
    }
    let digest = SHA512.hash(data: jsonStringWithSaltBytes)
    let hashBytes = digest.bytes
    var hashWithSaltBytes: [UInt8] = Array(repeating: 0, count: (hashBytes.count + saltBytes.count))
    
    for index in 0..<hasBytes.count {
        hashWithSaltBytes[index] = hashBytes[index]
    }
    for index in 0..<saltBytes.count {
        hashWithSaltBytes[hashBytes.count + index] = saltBytes[index]
    }
  
    let FinalsaltData = Data(hasWithSaltBytes)
    let finalHashString = FinalsaltData.base64EncodedString()
    
    return finalHashString ?? ""
}
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