question: private void computeEncryptionKey ( ) throws PdfSecurityException { final MessageDigest md ; final byte [ ] key = getPaddedKey ( encryptionPassword , encryptionPassword ) ; try { md = MessageDigest . getInstance ( "MD5" ) ; encryptionKey = md . digest ( key ) ; if ( rev >= 3 ) { for ( int ii = 0 ; ii < 50 ; ii ++ ) { encryptionKey = md . digest ( encryptionKey ) ; } } } catch ( final Exception e ) { throw new PdfSecurityException ( "Exception " + e + " generating encryption key" ) ; } }
target:  set the key value