iphone - AES-256 encryption on iOS not producing same result as openssl -

i have been looking , looking @ hours. desperately trying ios encrypt short piece of text using aes-256 encryption can decrypted openssl.

straight forward? nope.

the code i've found ios not compatible keys , ivs openssl, i've had adapt it, it's plainly not working.

so here code encrypt using... passing in string encrypt (datastring) string key (key) , string initialisation vector (iv)...

- (nsdata *)aes256encrypt:(nsstring *)datastring withkey:(nsstring *)key iv:(nsstring *)iv {      // 'key' should 32 bytes aes256, null-padded otherwise     //char keyptr[kcckeysizeaes256+1]; // room terminator (unused)     //bzero(keyptr, sizeof(keyptr)); // fill zeroes (for padding)      // fetch key data     //[key getcstring:keyptr maxlength:sizeof(keyptr) encoding:nsutf8stringencoding];      //nslog(@"keyptr: '%s'", keyptr);      nsdata *keydata = [key datausingencoding:nsutf8stringencoding];     nslog(@"keyptr: '%s'", keydata.bytes);     nsdata *datatoencrypt = [datastring datausingencoding:nsutf8stringencoding];     nsdata *ivdata = [iv datausingencoding:nsutf8stringencoding];      nsuinteger datalength = [datatoencrypt length];      //see doc: block ciphers, output size less or      //equal input size plus size of 1 block.     //that's why need add size of 1 block here     size_t buffersize = datalength + kccblocksizeaes128;     void *buffer = malloc(buffersize);      size_t numbytesencrypted = 0;     cccryptorstatus cryptstatus = cccrypt(kccencrypt, kccalgorithmaes128, kccoptionpkcs7padding,                                           keydata.bytes, kcckeysizeaes256,                                           ivdata.bytes, // initialisation vector                                           datatoencrypt.bytes,                                            datatoencrypt.length, /* input */                                           buffer, buffersize, /* output */                                           &numbytesencrypted);     if (cryptstatus == kccsuccess) {         //the returned nsdata takes ownership of buffer , free on deallocation         return [nsdata datawithbytesnocopy:buffer length:numbytesencrypted];     }      free(buffer); //free buffer;     return nil; } 

for same string encode, not produce same value when using openssl same key , iv... e.g. command line:

openssl enc -aes-256-cbc -e -in secrets.txt -a -iv 0000 -k 0000 -p 

secrets.txt text file containing string encrypted

this outputs this:

salt=3c66000000000000 key=0000000000000000000000000000000000000000000000000000000000000000 iv =00000000000000000000000000000000 qtmfgtaxbf8yyh27zdrciq== 

and decrypt, opposite operation (assuming encrypted last line of data above in test.secrets.out)

openssl enc -aes-256-cbc -d -in test.secrets.out -a -iv 0000 -k 0000 -p  salt=3c66000000000000 key=0000000000000000000000000000000000000000000000000000000000000000 iv =00000000000000000000000000000000 < text of secrets.txt file > 

now, if use key , iv of 4 chars, doesn't encode correctly in ios. if use full length key , iv, doesn't encode correctly either.

basically, check see if send piece of encrypted data right piece of data.

what missing?

some code i've looked through try find answer...

http://robnapier.net/blog/aes-commoncrypto-564

https://github.com/rnapier/rncryptor

http://pastie.org/426530

have searched extensively on here , cannot find answer.

any appreciated.

openssl has unique (read "not close standard, , not particularly secure") method converting passwords iv , key. if @ rnopensslcryptor, you'll see algorithm used:

// aes-128: // // key = md5(password + salt) // iv = md5(key + password + salt)  // // aes-256: // // hash0 = '' // hash1 = md5(hash0 + password + salt) // hash2 = md5(hash1 + password + salt) // hash3 = md5(hash2 + password + salt) // hash4 = md5(hash3 + password + salt) // // key = hash1 + hash2 // iv = hash3 + hash4 //  // file format: // // |salted___|<salt>|<ciphertext>| // 

using rnopensslcryptor allows rncryptor support openssl format. in midst of reworking code on async branch support async operations, , branch doesn't yet support openssl, plan rework shortly (by mid-july 2012).

if want code implements own use, @ keyforpassword:salt: , ivforkey:password:salt:.

note the openssl file format has several security problems , don't recommend if can avoid it. not use kdf generate key, not have random iv should, , provides no hmac authentication. these security problems why designed different file format, hated creating "yet incompatible container."