What is maximum number of characters in password

[macattak1]

I would like to use as large a string as possible. But I am having a heck of a time trying to figure it out.

[Stefan - PDF-XChange]

Hello macattak1,

You can use a password with any length you like, but reading the PDF specification - if you use a password shorter than 32 bytes when encrypting your document this password would be filled up to 32 bytes, and if it is longer - it will be truncated to 32 bytes.

Code: Select all

Algorithm 3.2  Computing an encryption key
1.    Pad or truncate the password string to exactly 32 bytes. If the password string is 
more than 32 bytes long, use only its first 32 bytes; if it is less than 32 bytes long, 
pad it by appending the required number of additional bytes from the beginning 
of the following padding string: 
<  28  BF  4E  5E  4E  75  8A  41  64  00  4E  56  FF  FA  01  08  
     2E  2E  00  B6  D0  68  3E  80  2F  0C  A9  FE  64  53  69  7A   >

So if you are using a single byte characters the "optimal" password would be 32 chars, and if you are using multibyte chars (e.g. Chinese, Japanese) the "optimal" password length would be less.
I am putting "optimal" in quotes on purpose, as any strong alphanumeric password with a length of e.g. 12 chars would be sufficient unless you are working with e.g. Top Secret documents but then I would presume the security would be on more than the default PDF level.

Best,
Stefan

[macattak1]

Thanks Stefan.

So an English character is considered 1 byte? Am I understanding that correctly?

If so, why can I only get 24? Are special characters !@#$%^&*()_+ considered more than one byte for any of them?

Thanks!
Peace and Blessings

[Ivan - Tracker Software]

If so, why can I only get 24?

Can you say where? Is your problem related to any of Tracker's product?