Creating iOS SHA1 Hash with UTF-8 characters - objective-c

Question

I'm using this code to create hash from giving string to devolving IOS App.
-(NSString*) sha1:(NSString*)input
{
const char *cstr = [input cStringUsingEncoding:NSUTF8StringEncoding];
NSData *data = [NSData dataWithBytes:cstr length:input.length];
uint8_t digest[CC_SHA1_DIGEST_LENGTH];
CC_SHA1(data.bytes, data.length, digest);
NSMutableString* output = [NSMutableString stringWithCapacity:CC_SHA1_DIGEST_LENGTH * 2];
for(int i = 0; i < CC_SHA1_DIGEST_LENGTH; i++)
[output appendFormat:#"%02x", digest[i]];
return output;
}
my PHP code is
sha1(json_encode($array));
I have string that contain Arabic languages.
when I create hash from English string and compare it with hash created from php code under Ubuntu*strong text* the result will be the same.
but when I create the hash with Arabic character it will and compare it with hash created from php code does't mach the result.
so what is the man problem with this code.
Thanks

Answer 1

input.length is the number of characters, not the number of bytes, the difference is that many bytes under UTF8 encoding are multiple bytes in length.
Replace:
const char *cstr = [input cStringUsingEncoding:NSUTF8StringEncoding];
NSData *data = [NSData dataWithBytes:cstr length:input.length];
with the NSString method:
NSData *data = [input dataUsingEncoding: NSUTF8StringEncoding];
There is no need for the intermediate const char *cstr.

Answer 2

I found my problem that come from my PHP json_encode($array) function.
so I found this function in http://php.net/manual/en/function.json-encode.php that encode my json with UTF-8 character
function my_json_encode($arr)
{
//convmap since 0x80 char codes so it takes all multibyte codes (above ASCII 127). So such characters are being "hidden" from normal json_encoding
array_walk_recursive($arr, function (&$item, $key) { if (is_string($item)) $item = mb_encode_numericentity($item, array (0x80, 0xffff, 0, 0xffff), 'UTF-8'); });
return mb_decode_numericentity(json_encode($arr), array (0x80, 0xffff, 0, 0xffff), 'UTF-8');
}
EX:
sha1(my_json_encode($newArray)