ios AES256解密方法

1 首先创建一个NSString分类
这是.h文件

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSString (EncryptVerbHandle)
/**
 AES解密算法
 @param str 要解密的字符串
 @param keyStr: 解码key（需要和后台协商定义）
 @return 解密后的字符串
 */
+ (NSString *) aes256_decrypt:(NSString *) str andkey:(NSString *)keyStr;

@end

NS_ASSUME_NONNULL_END

2 这是.m文件

#import "NSString+EncryptVerbHandle.h" //AES256加密

@implementation NSString (EncryptVerbHandle)
// Aes解密
+ (NSString *)aes256_decrypt:(NSString *)str andkey:(NSString *)keyStr{
    //先对加密的字符串进行base64解码
    NSData *keyData = [[NSData alloc] initWithBase64EncodedString:str options:0];
    char keyPtr[kCCKeySizeAES256 + 1];
    bzero(keyPtr, sizeof(keyPtr));
    /*AES加密与解密的秘钥，需要与后台协商共同定义，保持与后台的秘钥相同*/
    [keyStr getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    NSUInteger dataLength = [keyData length];
    size_t bufferSize           = dataLength + kCCBlockSizeAES128;
    void* buffer                = malloc(bufferSize);
    size_t numBytesDecrypted    = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionPKCS7Padding|kCCOptionECBMode,
                                          keyPtr,
                                          kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [keyData bytes],
                                          dataLength, /* input */
                                          buffer,
                                          bufferSize, /* output */
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        NSData *data = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        return result;
    }else{
        free(buffer);
        return nil;
    }
}
@end

3 调用
先引入 #import "NSString+EncryptVerbHandle.h" //AES解密

NSString *mb256Str = [NSString aes256_decrypt:@"xxx" andkey:@"xxx"];
//mb256Str就是解码完的参数

要注意这几个参数，参数不同，解密的规则不同
kCCAlgorithmAES128
kCCKeySizeAES256