ios - How can I generate this kind of string pattern as key for encryption -

hi trying generate kind of nsstring pattern real string "abcdefgh" want take corresponding bytes using

nsdata *data=[mystring datausingencoding:nsutf8stringencoding] nslog(@"%d",[data bytes]);   

copy these values byte array , limit total array size 24bit.

then want create following pattern

"abcdefgh efghabcd hgfedcba" 

how can generate kind of key ?

please me

i think work. logic reversedstring taken this answer

#import "nsstring+customcrypto.h"  @implementation nsstring (customcrypto)  - (nsstring *)reversedstring{      nsmutablestring *reversedstring = [nsmutablestring stringwithcapacity:[self length]];      [self enumeratesubstringsinrange:nsmakerange(0,[self length])                                  options:(nsstringenumerationreverse | nsstringenumerationbycomposedcharactersequences)                               usingblock:^(nsstring *substring, nsrange substringrange, nsrange enclosingrange, bool *stop) {                                   [reversedstring appendstring:substring];                               }];      return [nsstring stringwithstring:reversedstring]; }  - (nsstring *)splicedstring{      nsinteger index = [self length]/2;      nsstring *substring = [self substringfromindex:index];     nsstring *secondstring = [self substringtoindex:index];      return [substring stringbyappendingstring:secondstring]; }  - (nsstring *)customcryptostring{      nsstring *splicedstring = [self splicedstring];     nsstring *reversedstring = [self reversedstring];      return [nsstring stringwithformat:@"%@ %@ %@",self, splicedstring, reversedstring]; } 

call category method of string

nslog(@"%@",[@"abcdefgh" customcryptostring]); 

output : abcdefgh efghabcd hgfedcba