SQLCipher legacy

[little-brother]

i'm a little confused.
If I set legacy as 0 for cipher=sqlcipher then what option should/can I set?
And what are their default values?

How is legacy related to cipher-compatibility?

[utelle]

If I set legacy as 0 for cipher=sqlcipher then what option should/can I set?
And what are their default values?

The parameters you can set for the SQLCipher cipher are described in the cipher documentation for SQLCipher. At the bottom of the page you find a table with the default values of the parameters depending on the SQLCipher version.

If the parameter legacy is set to 0, then the default parameter values correspond typically to those of SQLCipher version 4. However, this can be changed at compile time by selecting a different default version (by defining symbol SQLCIPHER_VERSION_DEFAULT).

Note: Please keep in mind that using legacy=0 results in database files that are not compatible with the original SQLCipher library. If you need compatibility with the original SQLCipher library, you must set legacy to the SQLCipher version number you want compatibility with.

How is legacy related to cipher-compatibility?

In fact, legacy is equivalent to cipher_compatibility, except for the case legacy=0.

legacy=0 was introduced to obey the constraint of the official SQLite Encryption Extension (SEE) that bytes 16 to 23 of the database header are not encrypted, because those bytes are accessed by SQLite before any encryption extension gets a chance to decrypt them. The original libraries for the ciphers SQLCipher and sqleet chose to ignore this constraint, although this can lead to invalid database files (even though the chance for this to happen is only 1 : 8192).

[little-brother]

Thanks!

I thought that versions are different codecs but there are simple pre-defined profiles. So if I call pragma legacy=2 then all parameters will be switched to v2-column. But if I change legacy to 0 then no one parameter will be changed except legacy (and legacy_page_size will be ignored).

[utelle]

I thought that versions are different codecs but there are simple pre-defined profiles.

Right.

So if I call pragma legacy=2 then all parameters will be switched to v2-column.

Yes, exactly. pragma legacy=2 sets the parameters as required by SQLCipher version 2. If non-default parameters were used for an existing database file created with the original SQLCipher library, they have to be adjusted after calling pragma legacy=2.

But if I change legacy to 0 then no one parameter will be changed except legacy (and legacy_page_size will be ignored).

Correct. pragma legacy=0 just turns legacy mode off and uses the other parameter settings as they are.

The parameter legacy_page_size is required only for legacy SQLCipher database files, because the page size is encoded within the bytes 16 to 23 of the database header. Since the original SQLCipher library encrypts those bytes, the page size value - as read by SQLite - is usually invalid, and therefore SQLite assumes the default page size, which may not be the page size used by SQLCipher.

[little-brother]

Thanks, again. The question is closed for me.