对于web，安全是一个永久的话题，所以ASP.NET Core数据保护提供了一个简单，易用的加密API，可以用来保护数据，密钥管理和轮换。

ASP.NET Core的数据保护是根据本机的一个key来生成加密码，然后再用这个key来解密，如果key不一样，解密失败。默认情况下这个key的有效期是90天，当然这个值是可以被改变的。

默认数据保护key存放的位置，C:\Users\用户\AppData\Local\ASP.NET\DataProtection-Keys，如：key-a2b3132b-444b-4cfa-8530-922b7e991cd9.xml，是一个xml文件，里面记录了这个key的一些信息，创建时间，激活时间，过期时间，和加解密数据所用的命名空间，加密方式等信息，如下：

<?xml version="1.0" encoding="utf-8"?>
<key id="a2b3132b-444b-4cfa-8530-922b7e991cd9" version="1"><creationDate>2022-02-10T13:41:14.7492868Z</creationDate><activationDate>2022-02-10T13:41:14.7421157Z</activationDate><expirationDate>2022-05-11T13:41:14.7421157Z</expirationDate><descriptor deserializerType="Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption.ConfigurationModel.AuthenticatedEncryptorDescriptorDeserializer, Microsoft.AspNetCore.DataProtection, Version=6.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"><descriptor><encryption algorithm="AES_256_CBC" /><validation algorithm="HMACSHA256" /><encryptedSecret decryptorType="Microsoft.AspNetCore.DataProtection.XmlEncryption.DpapiXmlDecryptor, Microsoft.AspNetCore.DataProtection, Version=6.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" xmlns="http://schemas.asp.net/2015/03/dataProtection"><encryptedKey xmlns=""><!-- This key is encrypted with Windows DPAPI. --><value>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</value></encryptedKey></encryptedSecret></descriptor></descriptor>
</key>

使用数据保护的代码也很简单，注入DataProtection服务就可以，只需要使用服务时，通过IDataProtectionProvider创建一个数据保护对象，在创建时可以添加目标字符串参数，来防隔离不同的目标字符串加密的数据，所以key和这个目标字符串都能起到隔离作用。

using Microsoft.AspNetCore.DataProtection;var builder = WebApplication.CreateBuilder(args);
//通过SetDefaultKeyLifetime更改默认值90天
builder.Services.AddDataProtection().SetDefaultKeyLifetime(TimeSpan.FromDays(10));
var app = builder.Build();app.MapGet("/encrypt/{str}", (IDataProtectionProvider provider, ILogger<Program> logger, string str) =>
{var protector = provider.CreateProtector("a.b.c");var sec = protector.Protect(str);logger.LogInformation(sec);return "加密：" + sec;
});
app.MapGet("/decrypt/{sec}", (IDataProtectionProvider provider, ILogger<Program> logger, string sec) =>
{var protector = provider.CreateProtector("a.b.c");var str = protector.Unprotect(sec);logger.LogInformation(str);return "解密：" + str;
});app.Run();

上面代码只是实现了单机部署，如果集群部署，比如k8s中的不同pod，生成的key分别保存在自己的pod里，那么外部访问又是随机分配的，这时就会频繁出现解密失败的情况，这就要集中管理key了，用redis或数据库都可以，这里用到的是SqlServer，首先创建存key的表，如下：

CREATE TABLE [dbo].[DataProtectionKeys1]([ID] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY ,[FriendlyName] [varchar](64) NULL,[Xml] [text] NULL)

当有key保存进来时的结果如下：

其中字段key存的值如下，与本地文件存储的是一样的。

<key id="a32def14-9156-4c5e-946c-d3aa5b1a1743" version="1"> <creationDate>2022-02-10T14:20:37.5680295Z</creationDate>  <activationDate>2022-02-10T14:20:36.5853181Z</activationDate>  <expirationDate>2022-05-11T14:20:36.5853181Z</expirationDate>  <descriptor deserializerType="Microsoft.AspNetCore.DataProtection.AuthenticatedEncryption.ConfigurationModel.AuthenticatedEncryptorDescriptorDeserializer, Microsoft.AspNetCore.DataProtection, Version=6.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60"> <descriptor> <encryption algorithm="AES_256_CBC"/>  <validation algorithm="HMACSHA256"/>  <masterKey xmlns:p4="http://schemas.asp.net/2015/03/dataProtection" p4:requiresEncryption="true">  <!-- Warning: the key below is in an unencrypted form. -->  <value>gO70+leJQM8NJopS5VmMy+qkz0j+I9diBoCnxkqGxpqdXmyTULgAhMyu+3S4SJ0vjsx8Hxc+d/ipUgDBnkuQNw==</value> </masterKey> </descriptor> </descriptor>
</key>

这时，代码需要支持EF，所以引入如下NuGet包

Microsoft.AspNetCore.DataProtection Microsoft.AspNetCore.DataProtection.EntityFrameworkCore Microsoft.EntityFrameworkCore

Microsoft.EntityFrameworkCore.SqlServer

代码要换成EF方式持久化key，要注入EF的Context，然后注入数据保护对象时指明持久化的方式：

using Microsoft.AspNetCore.DataProtection;
using Microsoft.AspNetCore.DataProtection.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;var builder = WebApplication.CreateBuilder(args);builder.Services.AddDbContext<DataProtContext>(options =>options.UseSqlServer(builder.Configuration.GetConnectionString("DataProtDB")));
builder.Services.AddDataProtection().PersistKeysToDbContext<DataProtContext>();
var app = builder.Build();app.MapGet("/encrypt/{str}", (IDataProtectionProvider provider, ILogger<Program> logger, string str) =>
{var protector = provider.CreateProtector("a.b.c");var sec = protector.Protect(str);logger.LogInformation(sec);return "加密：" + sec;
});
app.MapGet("/decrypt/{sec}", (IDataProtectionProvider provider, ILogger<Program> logger, string sec) =>
{var protector = provider.CreateProtector("a.b.c");var str = protector.Unprotect(sec);logger.LogInformation(str);return "解密：" + str;
});app.Run();class DataProtContext : DbContext, IDataProtectionKeyContext
{public DbSet<DataProtectionKey> DataProtectionKeys { get; set; }public DataProtContext(DbContextOptions<DataProtContext> options): base(options){}
}

加密结果：

解密结果：

如果生成的加密串需要时效性，需要把生成的Protector转成TimeLimitedDataProtector来加解密，如下：

……
app.MapGet("/encrypt/{str}", (IDataProtectionProvider provider, ILogger<Program> logger, string str) =>
{var protector = provider.CreateProtector("a.b.c");var sec = protector.ToTimeLimitedDataProtector().Protect(str, TimeSpan.FromSeconds(30));logger.LogInformation(sec);return "加密：" + sec;
});
app.MapGet("/decrypt/{sec}", (IDataProtectionProvider provider, ILogger<Program> logger, string sec) =>
{var protector = provider.CreateProtector("a.b.c");var str = protector.ToTimeLimitedDataProtector().Unprotect(sec);logger.LogInformation(str);return "解密：" + str;
});……

如果加密串过期提交，报错如下：