Encryption.h文件

 

 

#import <Foundation/Foundation.h>

 

@class NSString;

 

@interface NSData (Encryption)

 

- (NSData *)AES256EncryptWithKey:(NSString *)key;   //加密

- (NSData *)AES256DecryptWithKey:(NSString *)key;   //解密

- (NSString *)newStringInBase64FromData;            //追加64编码

+ (NSString*)base64encode:(NSString*)str;           //同上64编码

 

@end

 

------------------------------------------------------------------------------------------------

 

Encryption.m文件

 

#import "Encryption.h"

#import <CommonCrypto/CommonCryptor.h>

 

 

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

 

@implementation NSData (Encryption)

 

- (NSData *)AES256EncryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    
    //See the doc: For block ciphers, the output size will always be less than or 
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesEncrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                     keyPtr, kCCKeySizeAES256,
                                     NULL /* initialization vector (optional) */,
                                     [self bytes], dataLength, /* input */
                                     buffer, bufferSize, /* output */
                                     &numBytesEncrypted);
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }

    free(buffer); //free the buffer;
    return nil;
}

- (NSData *)AES256DecryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)
    
    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
    
    NSUInteger dataLength = [self length];
    
    //See the doc: For block ciphers, the output size will always be less than or 
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);
    
    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                     keyPtr, kCCKeySizeAES256,
                                     NULL /* initialization vector (optional) */,
                                     [self bytes], dataLength, /* input */
                                     buffer, bufferSize, /* output */
                                     &numBytesDecrypted);
    
    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }
    
    free(buffer); //free the buffer;
    return nil;
}
 

- (NSString *)newStringInBase64FromData            //追加64编码

{

    NSMutableString *dest = [[NSMutableString alloc] initWithString:@""];

    unsigned char * working = (unsigned char *)[self bytes];

    int srcLen = [self length];

    for (int i=0; i<srcLen; i += 3) {

        for (int nib=0; nib<4; nib++) {

            int byt = (nib == 0)?0:nib-1;

            int ix = (nib+1)*2;

            if (i+byt >= srcLen) break;

            unsigned char curr = ((working[i+byt] << (8-ix)) & 0x3F);

            if (i+nib < srcLen) curr |= ((working[i+nib] >> ix) & 0x3F);

            [dest appendFormat:@"%c", base64[curr]];

        }

    }

    return dest;

}

 

+ (NSString*)base64encode:(NSString*)str

{

    if ([str length] == 0)

        return @"";

    const char *source = [str UTF8String];

    int strlength  = strlen(source);

    char *characters = malloc(((strlength + 2) / 3) * 4);

    if (characters == NULL)

        return nil;

    NSUInteger length = 0;

    NSUInteger i = 0;

    while (i < strlength) {

        char buffer[3] = {0,0,0};

        short bufferLength = 0;

        while (bufferLength < 3 && i < strlength)

            buffer[bufferLength++] = source[i++];

        characters[length++] = base64[(buffer[0] & 0xFC) >> 2];

        characters[length++] = base64[((buffer[0] & 0x03) << 4) | ((buffer[1] & 0xF0) >> 4)];

        if (bufferLength > 1)

            characters[length++] = base64[((buffer[1] & 0x0F) << 2) | ((buffer[2] & 0xC0) >> 6)];

        else characters[length++] = '=';

        if (bufferLength > 2)

            characters[length++] = base64[buffer[2] & 0x3F];

        else characters[length++] = '=';

    }

    NSString *g = [[[NSString alloc] initWithBytesNoCopy:characters length:lengthencoding:NSASCIIStringEncoding freeWhenDone:YES] autorelease];

    return g;

}

 

 

@end

 

------------------------------------------------------------------------------------------------

 

测试代码

 

 

#import "Encryption.h"
 

    NSString *key = @"my password";

    NSString *secret = @"text to encrypt";

    //加密

    NSData *plain = [secret dataUsingEncoding:NSUTF8StringEncoding];

    NSData *cipher = [plain AES256EncryptWithKey:key];

    NSLog(@"%@",[[cipher newStringInBase64FromData] autorelease]);

    printf("%s\n", [[cipher description] UTF8String]);

    NSLog(@"%@", [[[NSString alloc] initWithData:cipher encoding:NSUTF8StringEncoding] autorelease]);//打印出null,这是因为没有解密。

    //解密

    plain = [cipher AES256DecryptWithKey:key];

    printf("%s\n", [[plain description] UTF8String]);

    NSLog(@"%@", [[[NSString alloc] initWithData:plain encoding:NSUTF8StringEncoding] autorelease]);

    //打印出secret的内容,用密码解密过了。如果使用错误的密码，则打印null

 

 

i am new in Objective c.My problem is how to convert image to Byte array[Encoding].Similarly how to convert Byte array to Image[Decoding]...In C i am using the Following code for Encoding and Decoding purpose...
#include <stdio.h>
#include <stdlib.h>

/*
** Translation Table as described in RFC1113
*/
static const char cb64[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuv wxyz0123456789+/";

/*
** Translation Table to decode (created by author)
*/
static const char cd64[]="|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW $$$$$$XYZ[\\]^_`abcdefghijklmnopq";

/*
** encodeblock
**
** encode 3 8-bit binary bytes as 4 '6-bit' characters
*/
void encodeblock( unsigned char in[3], unsigned char out[4], int len )
{
out[0] = cb64[ in[0] >> 2 ];
out[1] = cb64[ ((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4) ];
out[2] = (unsigned char) (len > 1 ? cb64[ ((in[1] & 0x0f) << 2) | ((in[2] & 0xc0) >> 6) ] : '=');
out[3] = (unsigned char) (len > 2 ? cb64[ in[2] & 0x3f ] : '=');
}

/*
** encode
**
** base64 encode a stream adding padding and line breaks as per spec.
*/
void encode( FILE *infile, FILE *outfile, int linesize )
{
unsigned char in[3], out[4];
int i, len, blocksout = 0;

while( !feof( infile ) ) {
len = 0;
for( i = 0; i < 3; i++ ) {
in[i] = (unsigned char) getc( infile );
if( !feof( infile ) ) {
len++;
}
else {
in[i] = 0;
}
}
if( len ) {
encodeblock( in, out, len );
for( i = 0; i < 4; i++ ) {
putc( out[i], outfile );
}
blocksout++;
}
if( blocksout >= (linesize/4) || feof( infile ) ) {
if( blocksout ) {
fprintf( outfile, "\r\n" );
}
blocksout = 0;
}
}
}

/*
** decodeblock
**
** decode 4 '6-bit' characters into 3 8-bit binary bytes
*/
void decodeblock( unsigned char in[4], unsigned char out[3] )
{ 
out[ 0 ] = (unsigned char ) (in[0] << 2 | in[1] >> 4);
out[ 1 ] = (unsigned char ) (in[1] << 4 | in[2] >> 2);
out[ 2 ] = (unsigned char ) (((in[2] << 6) & 0xc0) | in[3]);
}

/*
** decode
**
** decode a base64 encoded stream discarding padding, line breaks and noise
*/
void decode( FILE *infile, FILE *outfile )
{
unsigned char in[4], out[3], v;
int i, len;

while( !feof( infile ) ) {
for( len = 0, i = 0; i < 4 && !feof( infile ); i++ ) {
v = 0;
while( !feof( infile ) && v == 0 ) {
v = (unsigned char) getc( infile );
v = (unsigned char) ((v < 43 || v > 122) ? 0 : cd64[ v - 43 ]);
if( v ) {
v = (unsigned char) ((v == '$') ? 0 : v - 61);
}
}
if( !feof( infile ) ) {
len++;
if( v ) {
in[ i ] = (unsigned char) (v - 1);
}
}
else {
in[i] = 0;
}
}
if( len ) {
decodeblock( in, out );
for( i = 0; i < len - 1; i++ ) {
putc( out[i], outfile );
}
}
}
}

But i don't know in objective c...Pls help me to sort out this issue...

Thanks
jayaprakash S