  In this paper, we propose a session based bit level symmetric key
cryptographic technique and it is termed as Spiral Matrix Based Bit Orientation
Technique (SMBBOT). SMBBOT consider the input plain text as binary bit stream.
During encryption this stream is chopped into manageable sized blocks with
variable lengths. Bits of these blocks are taken from MSB to LSB to fit into a
square matrix of suitable order following the concept of Spiral matrix. This
square matrix splits into 2x2 sub-matrices. Bits are taken column-wise from all
2x2 sub-matrices to form the encrypted binary string. Cipher text is generated
from this encrypted binary string. Combination of values of block length and
no. of blocks of a session generates the session key for SMBBOT. For decryption
the cipher text is considered as binary bit string. Processing the session key
information, this binary string is broken down into predefined blocks. Bits of
these blocks are taken from MSB to LSB to fit column-wise into 2x2 square
matrices. Using these sub-matrices a single square matrix with suitable order
is formed. The decrypted binary string is formed after taking the bits from the
square matrix following the reverse concept of Spiral Matrix. The plain text is
regenerated from decrypted binary string. A comparison of SMBBOT with existing
and industrially accepted TDES and AES has been done.
