I am just working on a (Spanish + Italian) -> English translation of
the Mediterranian MOSC tools.

It is a well known fact that Seca2 is basically Seca1 with most
EMMs and ECMs superencrypted.

According to Italian and Spanish boards the superencryption of the (V7.0)
is a modified CBC (chain block cipher) which in it's turn is a modifed DES
symmetric encryption.

CBC is modified the following way:

A 16 bit checksum of each encrpypted 8 byte cipher block is built.
An offset is calculated: 16 bit-checksum of the cipher block mod 4000(hex).
An 8 byte mask is taken from the offset address of the Mask Table
(aka Chain Table).

In standard DES-CBC, the base DES encryption function is applied to the XOR of
each plaintext block with the previous ciphertext block to yield the
ciphertext for the current block.

In V7.0 modified DES-CBC the base DES encryption function is applied to the
XOR of each plaintext block with:

((the previous ciphertext) XOR (mask obtained from MT[offset]))

to yield the ciphertext for the current block.

The contents of the Italian and Spanish V7.0 mask tables are well known and
published all over the internet. (Homealone, Escritura Controlada)

Both mask tables have a size of 128 Kbytes but the Spanish MT
can be easily condensed to 16 KBytes due to its regular structure.