Ver 5 Security Question

[Peter.Greulich]

I understand that v.5 will allow you to encrypt tables IF you assign a password to the database. Since I have my own password schema, will v.5 allow you to enter the database password in xbasic (say in the autoexec script)? Otherwise, users will have to enter two passwords, A5's and the custom one already implemented (or use v.5's password model).

OR, is there a way to encrypt tables w/o the database password?

Peter

[nick marodis]

RE: Ver 5 Security Question

peter this all i found on the subject


Encrypting Tables
Alpha Five allows you to encrypt tables so that people who do not know the password cannot read them. This is particularly important because Alpha Five uses a very common file format for its data, the .dbf format, which many programs can read. Once you have encrypted a table, other programs cannot read it.
After a table has been encrypted, it is displayed in the Control Panel with a lock on the icon. In addition, if the decryption key has not been set, a question mark is displayed on the icon, indicating that Alpha Five cannot read the table yet.

Icon for an encrypted table. Alpha Five can read the table because the decryption key has been set.
Icon for an encrypted table. Alpha Five cannot read the table because the decryption key has not yet been set.

Alpha Five provides several functions to encrypt and decrypt tables. These are described below.
NOTE While Alpha Five does provide the low level Xbasic commands described below to encrypt and decrypt tables, this is not the typical way in which encryption is used. It is more convenient to use the encrypt tables using the user interface commands. You can access the encryption feature once a Master Password has been set for the database (which is done using the Tools, Security command when the Control Panel has focus). Once the Master Password for the database has been set, you can use the Tools, Encrypt/Decrypt tables command to encrypt or decrypt tables. The Master Password is used as the encryption key for all tables. You would only use the Xbasic methods described below if you want to have more control over the encryption and decryption of tables than Alpha Five's built in security features offer.

.encrypt()
Syntax:
Flag = .encrypt([Encryption key])
Description:
Encrypts the table referenced by the object pointer, . Flag is .T. if the operation is successful. If Encryption key is not specified, Alpha Five uses the default encryption key. The default encryption key can be changed using the default_encryption_key_set() function.
Alpha Five requires exclusive access to the table in order to encrypt it.
Example:

'Encrypt a table using the default key
'-----------------------------------------------------------------
t = table.open("customer")
t.encrypt()
t.close()

'Encrypt a table using a specific key
'-----------------------------------------------------------------
t = table.open("customer")
t.encrypt("swordfish")
t.close()


See Also:
.memo_write_to_file()
.decrypt()
Syntax:
Flag = .decrypt()
Description:
Decrypts the table referenced by the object pointer, . Flag is .T. if the operation is successful.
Alpha Five requires exclusive access to the table in order to decrypt it.
Example:

'Decrypt a table
'-----------------------------------------------------------------
t = table.open("customer")
t.decrypt()
t.close()

See Also:
.memo_write_to_file()

default_encryption_key_set()
Syntax:
default_encryption_key_set(Encryption Key)
Description:
Sets the default key that Alpha Five will use to encrypt and decrypt tables. If the default encryption key is not set to the same key that was used to initially encrypt a table, the table's icon in the Control Panel is shown with a lock on it.
Example:

'Sets the encryption key to "Fish"
'-----------------------------------------------------------------
default_encryption_key_set("fish")

See Also:
.memo_write_to_file()




L .encrypted()
Returns .T. if table is encrypted, else returns .F.

Also added are a forth parameter (after alias) to table.open() and table.reset(), plus
a third parameter (after mode) to set.open()

This parameter is an optional encrytion_key which will be used to decode the file
during file reads.

There are new icons that display on the control panel for tables that are encrypted using
the default key, or some other key.

Tables that are encrypted using the default key appear with a padlock icon overlayed on
the standard table icon. These 'default' encrypted tables can be loaded, operated on etc
directly from a5, but the tables are inaccessable from other applications that read DBF
files.

Also - if the default key has not been set, Alpha five won't even be able to read them.

Tables that are encrypted with keys other than the default key (or if the default key hasn't
even been defined yet) - will show up with a padlock and a question mark icon.

If you wish to experiment with this feature, I would advise working on a 'copy' of your data -

I have found and fixed every problem I have encountered thus far (i.e, like appends etc,
which due to file handle duplication ended up mixing and matching encrypted data with
other data).

Here is a sample session - say you a table called "names.dbf" which is a list of
names that you want to protect from prying eyes.
in the interactive window
t = table.open("names")
t.encrypt("swordfish")
t.close()

If you look back at the control panel, you will notice that the icon for the table changed
to a table with a padlock and question mark -- this means that alpha five cannot load
the table because it is encrypted with a key, and there is no default key defined yet...
(Try clicking on the table or any of its associated layouts, you will encounter an error
- file is encrypted & you don't have the key!) -- if the icon doesn't show up immediatly, you
may need to click between panels,

however we can still use the table from xbasic...
t = table.open("names",0,"","swordfish")
t.fetch_first()
trace.writeln("I can see that the first name in names.dbf is "+t.name+" and you can't!")
t.close()

Now using tables from xbasic only is a little restrictive, so lets define the default key
from the interactive window:
default_encryption_key_set("swordfish")

You will notice after doing this that the table icon loses its question mark, and just has
a padlock -- this means that alpha five can use the DBF, but nobody else can (including
other sessions of A5 that don't know the encryption key value)...

Now if you click on browse/form append etc - they all work.
Now lets say you wanted to decrypt the file so that it was available publicly once again
t = table.open("names",0,"","swordfish")
t.decrypt()
t.close()

[Peter.Greulich]

RE: Ver 5 Security Question

Hello Nick,

Thanks a million. This is music to my ears! Just what I wanted.

Peter

[Sean Tucker]

RE: Ver 5 Security Question

When I tried to use this code I received the error:
encrypt method not found
Maybe I didn't understand the proper place for the code. I placed the code in the Code Editor in the Interactive window.

[Peter.Greulich]

RE: Ver 5 Security Question

It requires ver. 5 which is not available yet.