Someone please straighten me out about 128 bits versus 256 bits etc....

Don M

On my Mac I request an AES 128 bit key and this is what I get:

Mac-mini:~ Don$ openssl enc -aes-128-ecb -k secret -P -md sha1

salt=CB4965AB825F439A
key=4CE5696CBAA93AB93945829B4322BE78

It looks to me that the key is 256 bits (32 HEX bytes) long if I'm looking at it this way 16 bytes * 8 bits == 256 bits:

4C E5 69 6C BA A9 3A B9 39 45 82 9B 43 22 BE 78


Do I only use half of it for a 128 bit key?

Also what does "salt" mean?

SRLM

Don M wrote: »

It looks to me that the key is 256 bits (32 HEX bytes) long if I'm looking at it this way 16 bytes * 8 bits == 256 bits:

4C E5 69 6C BA A9 3A B9 39 45 82 9B 43 22 BE 78

A hex digit is 4 bits, not 8... So, 16 bytes * 8 bits == 256 bits 128 bits

D.P

SRLM wrote: »

A hex digit is 4 bits, not 8... So, 16 bytes * 8 bits == 256 bits 128 bits

And from the ssl manual:

"Note the -salt option. The salt is a set of random characters that OpenSSL combines with the password to create the encryption and authentication keys. This makes dictionary and brute force attacks considerably more difficult. Always use the -salt option. "

r.daneel

Each hex digit is 4 bits. You have 32 hex digits, so that'd be 32 * 4 = 128. Not sure where you're getting 256. 16 * 8 = 128, not 256.

Read about Salt here:

http://en.wikipedia.org/wiki/Salt_(cryptography)

Don M

Thanks everyone for straightening me out here... I was confusing a byte with a digit.