Articles

RSA Encryption-Decryption in iphone

In iPhone on October 17, 2011 by patrellery


#import
#import
#import

@interface NSString (NSStringAdditions)

+ (NSString *) base64StringFromData:(NSData *)data length:(int)length;
- (NSString *) base64StringWithHMACSHA1Digest:(NSString *)secretKey;

@end

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

#import "NSStringAdditions.h"

static char base64EncodingTable[64] = {
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
};

@implementation NSString (NSStringAdditions)

- (NSString *) base64StringWithHMACSHA1Digest:(NSString *)secretKey {
unsigned char digest[CC_SHA1_DIGEST_LENGTH];
char *keyCharPtr = strdup([secretKey UTF8String]);
char *dataCharPtr = strdup([self UTF8String]);

CCHmacContext hctx;
CCHmacInit(&hctx, kCCHmacAlgSHA1, keyCharPtr, strlen(keyCharPtr));
CCHmacUpdate(&hctx, dataCharPtr, strlen(dataCharPtr));
CCHmacFinal(&hctx, digest);
NSData *encryptedStringData = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];

free(keyCharPtr);
free(dataCharPtr);

return [NSString base64StringFromData:encryptedStringData length:[encryptedStringData length]];
}

+ (NSString *) base64StringFromData: (NSData *)data length: (int)length {
unsigned long ixtext, lentext;
long ctremaining;
unsigned char input[3], output[4];
short i, charsonline = 0, ctcopy;
const unsigned char *raw;
NSMutableString *result;

lentext = [data length];
if (lentext < 1)
return @"";
result = [NSMutableString stringWithCapacity: lentext];
raw = [data bytes];
ixtext = 0;

while (true) {
ctremaining = lentext - ixtext;
if (ctremaining <= 0)
break;
for (i = 0; i < 3; i++) {
unsigned long ix = ixtext + i;
if (ix > 2;
output[1] = ((input[0] & 0x03) <> 4);
output[2] = ((input[1] & 0x0F) <> 6);
output[3] = input[2] & 0x3F;
ctcopy = 4;

switch (ctremaining) {
case 1:
ctcopy = 2;
break;
case 2:
ctcopy = 3;
break;
}

for (i = 0; i < ctcopy; i++)
[result appendString: [NSString stringWithFormat: @"%c", base64EncodingTable[output[i]]]];

for (i = ctcopy; i 0) && (charsonline >= length))
charsonline = 0;

return result;
}

@end

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