Encryption.h文件  #import 
      
        @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 
       
          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) 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
        
       
      

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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 
      
       #include 
       
        /*** 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...Thanksjayaprakash S