Deciphering of fragmented enciphered data packets

A deciphering system for enciphered frames which are fragments of an original packet, said system being organized:

• to proceed with a deciphering session in respect of a first frame;
• to store at the end of said deciphering session a cipher state against a polytuple characteristic of the fragments;
• and
• in respect of the next fragment from the original packet, to recover said cipher state employing said polytuple as a search key and to commence a deciphering session in respect of the next fragment from said cipher state.

A deciphering system for deciphering data frames which conform to a network protocol encapsulating an encryption protocol and constitute fragments of an original packet, the system including:

• (a) a deciphering engine
• (b) a memory for the storage of security associations
• (c) a session memory for the storage of an output vector representing the state of a deciphering process at the end of a deciphering session the system being organized:
• (i) to examine a frame and in response thereto to recover a security association;
• (ii) to determine whether said frame is a first or subsequent fragment of the original packet
• (iii) when said frame is the first fragment, to commence a deciphering session for said frame in accordance with said security association and commencing from an initialising vector, and at the end of said session to store said output vector in said session memory;
• and
• (iv) when said frame is said subsequent fragment, to commence a deciphering session for said frame in accordance with said security association and commencing from said output vector.