从密钥字符串生成64字节长的NSData [英] Generating 64 bytes long NSData from key string

问题描述

我认为这会产生随机的64字节NSData。

  uint8_t buffer [64]; 
 SecRandomCopyBytes（kSecRandomDefault，64，缓冲区）; 
 NSData * keyData = [[NSData alloc] initWithBytes：buffer length：sizeof（buffer）]; 
  

我想生成64字节NSData，但不是随机数据。
如何使用给定的键生成64个字节的NSData，如com.this.is.akey。

尝试了这个，但它给了我错误的字节大小（不是64字节）。

  NSString * base64EncodedString = [[@somekey.heredataUsingEncoding：NSUTF8StringEncoding] base64EncodedStringWithOptions：0 ]。 
 NSData * encodedData = [[NSData alloc] initWithBase64EncodedString：base64EncodedString 
 options：0]; 
  

解决方案

您可以使用 NSString dataUsingEncoding：] 将 NSString 转换为 NSData 。

  NSString * key = @com.this.is.akey; 
 NSData * keyData = [key dataUsingEncoding：NSASCIIStringEncoding]; 
  

如果数据长度小于或大于64字节，则应该将数据填充或截断64字节。

  if（keyData.length！= 64）{
 NSMutableData * mutableData = keyData.mutableCopy; 
 mutableData.length = 64; 
 keyData = mutableData.copy; 
} 
  

然后，您可以传递 NSData object to RLMRealmConfiguration.encryptionKey 。

  RLMRealmConfiguration * config = [RLMRealmConfiguration defaultConfiguration]; 
 config.encryptionKey = keyData; 
 
 NSError * error = nil; 
 RLMRealm * realm = [RLMRealm realmWithConfiguration：config error：& error]; 
  

I think this generates random 64 bytes NSData.

uint8_t buffer[64];
SecRandomCopyBytes(kSecRandomDefault, 64, buffer);
NSData *keyData = [[NSData alloc] initWithBytes:buffer length:sizeof(buffer)];

I want to generate 64 bytes NSData like this but not a random data. How can I generate 64 bytes NSData with a given key like "com.this.is.akey".

Tried this one but it gave me wrong bytes size(not 64 bytes).

NSString *base64EncodedString = [[@"somekey.here" dataUsingEncoding:NSUTF8StringEncoding] base64EncodedStringWithOptions:0];
NSData *encodedData = [[NSData alloc] initWithBase64EncodedString:base64EncodedString
                                                          options:0];

解决方案

You can use -[NSString dataUsingEncoding:] to convert NSString to NSData.

NSString *key = @"com.this.is.akey";
NSData *keyData = [key dataUsingEncoding:NSASCIIStringEncoding];

If length of the data is less or greater than 64 bytes, you should pad or truncate data to exact 64 bytes.

if (keyData.length != 64) {
    NSMutableData *mutableData = keyData.mutableCopy;
    mutableData.length = 64;
    keyData = mutableData.copy;
}

Then, you can pass the NSData object to RLMRealmConfiguration.encryptionKey.

RLMRealmConfiguration *config = [RLMRealmConfiguration defaultConfiguration];
config.encryptionKey = keyData;

NSError *error = nil;
RLMRealm *realm = [RLMRealm realmWithConfiguration:config error:&error];

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