IOS development diary 8-MD5 encryption, ios diary 8-MD5

IOS development diary 8-MD5 encryption, ios diary 8-MD5

Today, the blogger has a password encryption requirement and has encountered some difficulties. I would like to share with you the hope to make common progress.

MD5 encryption and SHA-1 encryption are two important encryption algorithms in the computer world. MD5 encryption is usually used to encrypt NSString, While SHA-1 encryption is usually used to encrypt URLs. Today we will share with you the MD5 encryption method.

To use MD5 encryption, add a category to NSString and import the header file <CommonCrypto/CommonDigest. h>.

Content in. h:

# Import <Foundation/Foundation. h>

# Import <CommonCrypto/CommonDigest. h>

 

@ Interface NSString (MD5encrypt)

-(NSString *) md5HexDigest;

@ End

. M content:

# Import "NSString + MD5encrypt. h"

 

@ Implementation NSString (MD5encrypt)

-(NSString *) md5HexDigest

{

Const char * original_str = [self UTF8String];

Unsigned char result [CC_MD5_DIGEST_LENGTH];

// CC_MD5 (original_str, strlen (original_str), result); the usage here is obviously incorrect. When original_str contains null characters (\ 0)

CC_MD5 (original_str, (unsigned int) self. length, result );

NSMutableString * hash = [NSMutableString string];

For (int I = 0; I <16; I ++)

[Hash appendFormat: @ "% 02X", result [I];

Return [hash lowercaseString];

}

@ End

Currently, MD5 is no longer absolutely secure. To solve this problem, We Can slightly improve MD5 to increase the difficulty of decryption:

1. Add Salt (Salt): Insert a random string at a fixed position in the plain text, and then perform MD5

2. Encryption first, followed by out-of-order: MD5 is performed on the plaintext, and then the characters in the encrypted MD5 string are in out-of-order.

In short, the objective is: Even if Hackers break the database, they cannot decrypt the correct plaintext.

/*** Use MD5 encryption directly */-(NSString *) digest :( NSString *) str {NSString * anwen = [str md5String];
NSLog (@ "% @-% @", str, anwen); return anwen;}/*** salt adding */-(NSString *) digest2 :( NSString *) str {str = [str stringByAppendingString: Salt]; NSString * anwen = [str md5String]; NSLog (@ "% @-% @", str, anwen); return anwen ;} /*** multiple MD5 */-(NSString *) digest3 :( NSString *) str {NSString * anwen = [str md5String]; anwen = [anwen md5String]; NSLog (@ "% @-% @", str, anwen); return anwen ;}
/*** Encrypt the data first and then unordered. We recommend that you use */-(NSString *) digest4 :( NSString *) str {NSString * anwen = [str md5String]; NSString * header = [anwen substringToIndex: 2]; NSString * footer = [anwen substringFromIndex: 2]; anwen = [footer stringByAppendingString: header]; NSLog (@ "% @-% @", str, anwen); return anwen ;}