最近在Android和IOS上都需要对用户的某些输入进行简单的加密，于是采用MD5加密方式。

• 首先将目的字符串加密一次，获得32位字符串
• 然后将32位字符串拆为2段，分别加密1次
• 最后将加密后的2段拼接，加密100次

下面是Android的Java部分和IOS的Objective-C部分

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import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;public class MD5Util{    public static String getMD5(String content) {        String s = makeMD5(content);        String s1 = null;        if (s != null) {            s1 = s.substring(0, 16);        }        String s2 = null;        if (s != null) {            s2 = s.substring(16, 32);        }        s1 = makeMD5(s1);        s2 = makeMD5(s2);        s = s1 + s2;        for (int i = 0; i < 100; i++) {            s = makeMD5(s);        }        return s;    }    private static String makeMD5(String content) {        try {            MessageDigest messageDigest = MessageDigest.getInstance("MD5");            messageDigest.update(content.getBytes());            return getHashString(messageDigest);        } catch (NoSuchAlgorithmException e) {            e.printStackTrace();        }        return null;    }    private static String getHashString(MessageDigest messageDigest) {        StringBuilder builder = new StringBuilder();        for (byte b : messageDigest.digest()) {            builder.append(Integer.toHexString(  ( b >> 4 ) & 0xf )  );            builder.append(Integer.toHexString(  b & 0xf )           );        }        return builder.toString();    }}

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#import "MD5Utils.h"#import 
    
     @implementation MD5Utils+(NSString*)MD5:(NSString *)input{    NSString* s = [self makeMd5:input];    NSString* s1 = [s substringToIndex:16];    NSString* s2 =[s substringFromIndex:16];    s1 = [self makeMd5:s1];    s2 = [self makeMd5:s2];    NSMutableString* md5String = [NSMutableString stringWithString:s1];    [md5String appendString:s2];    for(int i =0;i<100;i++){        md5String = [self makeMd5WithMutaleString:md5String];    }    return md5String;}+ (NSString*)makeMd5:(NSString*) str{    const char * pointer = [str UTF8String];    unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];    CC_MD5(pointer, (CC_LONG)strlen(pointer), md5Buffer);    NSMutableString *string = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)        [string appendFormat:@"%02x",md5Buffer[i]];    return string;}+ (NSMutableString*)makeMd5WithMutaleString:(NSMutableString*) str{    const char * pointer = [str UTF8String];    unsigned char md5Buffer[CC_MD5_DIGEST_LENGTH];    CC_MD5(pointer, (CC_LONG)strlen(pointer), md5Buffer);    NSMutableString *string = [NSMutableString stringWithCapacity:CC_MD5_DIGEST_LENGTH * 2];    for (int i = 0; i < CC_MD5_DIGEST_LENGTH; i++)        [string appendFormat:@"%02x",md5Buffer[i]];    return string;}@end