我应该使用哪个密钥在iOS密钥链中存储密码？

Apple GenericKeychain示例中的KeychainItemWrapper类使用kSecValueData密钥存储密码

但是参考文献

说kSecValueData是 在结果字典中用于SecItemCopyMatching或SecItemAdd，指示返回值的类型

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调用SecItemAdd创建密钥链项目时应使用哪个密钥？

您应使用kSecValue数据作为密钥来存储密码（NSData或CFDataRef格式）

本主题中的参考有点不清楚，kSecValueData键既可用作输出键，也可用作输入键。也就是说，当您查询一个keychain项（SecItemCopyMatching）并指定一个kSecReturnAttributes键时使用它，因此结果作为字典返回，密码将存储在该字典的kSecValueData键下。在向密钥链（SecItemAdd）添加项时也可以使用它，在调用该方法之前，将密码的NSData或CFDataRef值存储在kSecValueData键中

以下是两种情况的示例：

检索密码：

NSMutableDictionary *queryDictionary = [[NSMutableDictionary alloc] init];
[queryDictionary setObject: (__bridge id)kSecClassGenericPassword forKey: (__bridge id<NSCopying>)kSecClass];
[queryDictionary setObject:service forKey:kSecAttrService];
[queryDictionary setObject:account forKey:kSecAttrAccount];
// The result will be a dictionary containing the password attributes...
[queryDictionary setObject:YES forKey:(__bridge id<NSCopying>)(kSecReturnAttributes)];
// ...one of those attributes will be a kSecValueData with the password
[queryDictionary setObject:YES forKey:(__bridge id<NSCopying>)(kSecReturnData)];
OSStatus sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef)(queryDictionary), (CFTypeRef *)&result);
if (sanityCheck != noErr)
{
    NSDictionary * resultDict = (__bridge NSDictionary *)result;
    // here's the queried password value
    NSData *passwordValue = [resultDict objectForKey:(__bridge id)(kSecValueData)];
}

NSString *passwordString = @"my password value";
NSData *passwordData = [passwordString dataUsingEncoding:NSUTF8StringEncoding];
CFDictionaryRef result = nil;
NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] init];
[addDictionary setObject: (__bridge id)kSecClassGenericPassword forKey: (__bridge id<NSCopying>)kSecClass];
[addDictionary setObject:service forKey:kSecAttrService];
[addDictionary setObject:account forKey:kSecAttrAccount];

// here goes the password value
[addDictionary setObject:passwordData forKey:(__bridge id<NSCopying>)(kSecValueData)];

OSStatus sanityCheck = SecItemAdd((__bridge CFDictionaryRef)(queryDictionary), NULL)
if (sanityCheck != noErr)
{
   // if no error the password got successfully stored in the keychain
}

NSMutableDictionary*queryDictionary=[[NSMutableDictionary alloc]init]；
[queryDictionary setObject:（_桥id）kSecClassGenericPassword forKey:（_桥id）kSecClass]；
[queryDictionary设置对象：服务forKey:kSecAttrService]；
[queryDictionary setObject:account forKey:kSecAttrAccount]；
//结果将是一个包含密码属性的字典。。。
[queryDictionary setObject:YES forKey:（u桥id）（kSecReturnAttributes）]；
//…其中一个属性将是带有密码的kSecValueData
[queryDictionary setObject:YES forKey:（u桥id）（kSecReturnData）]；
OSStatus sanityCheck=SecItemCopyMatching（（uu桥CFDictionaryRef）（查询字典），（CFTypeRef*）和结果）；
如果（sanityCheck！=noErr）
{
NSDictionary*ResultDisct=（\u桥NSDictionary*）结果；
//这是查询到的密码值
NSData*passwordValue=[ResultDisct objectForKey:（u桥id）（kSecValueData）]；
}

添加密码：

NSMutableDictionary *queryDictionary = [[NSMutableDictionary alloc] init];
[queryDictionary setObject: (__bridge id)kSecClassGenericPassword forKey: (__bridge id<NSCopying>)kSecClass];
[queryDictionary setObject:service forKey:kSecAttrService];
[queryDictionary setObject:account forKey:kSecAttrAccount];
// The result will be a dictionary containing the password attributes...
[queryDictionary setObject:YES forKey:(__bridge id<NSCopying>)(kSecReturnAttributes)];
// ...one of those attributes will be a kSecValueData with the password
[queryDictionary setObject:YES forKey:(__bridge id<NSCopying>)(kSecReturnData)];
OSStatus sanityCheck = SecItemCopyMatching((__bridge CFDictionaryRef)(queryDictionary), (CFTypeRef *)&result);
if (sanityCheck != noErr)
{
    NSDictionary * resultDict = (__bridge NSDictionary *)result;
    // here's the queried password value
    NSData *passwordValue = [resultDict objectForKey:(__bridge id)(kSecValueData)];
}

NSString *passwordString = @"my password value";
NSData *passwordData = [passwordString dataUsingEncoding:NSUTF8StringEncoding];
CFDictionaryRef result = nil;
NSMutableDictionary *addDictionary = [[NSMutableDictionary alloc] init];
[addDictionary setObject: (__bridge id)kSecClassGenericPassword forKey: (__bridge id<NSCopying>)kSecClass];
[addDictionary setObject:service forKey:kSecAttrService];
[addDictionary setObject:account forKey:kSecAttrAccount];

// here goes the password value
[addDictionary setObject:passwordData forKey:(__bridge id<NSCopying>)(kSecValueData)];

OSStatus sanityCheck = SecItemAdd((__bridge CFDictionaryRef)(queryDictionary), NULL)
if (sanityCheck != noErr)
{
   // if no error the password got successfully stored in the keychain
}

NSString*passwordString=@“我的密码值”；
NSData*passwordData=[passwordString数据使用编码：NSUTF8StringEncoding]；
cfyref结果=零；
NSMutableDictionary*addDictionary=[[NSMutableDictionary alloc]init]；
[addDictionary setObject:（uu桥id）kSecClassGenericPassword forKey:（uu桥id）kSecClass]；
[addDictionary设置对象：服务forKey:kSecAttrService]；
[addDictionary setObject:account forKey:kSecAttrAccount]；
//下面是密码值
[addDictionary setObject:passwordData forKey:（u桥id）（kSecValueData）]；
OSStatus sanityCheck=SecItemAdd（（uu桥CFDictionaryRef）（queryDictionary），NULL）
如果（sanityCheck！=noErr）
{
//如果没有错误，密码将成功存储在钥匙链中
}

更好的代码，更少的bug，这里：