04-08-2012, 11:28 AM
Seminar Report Stenography
2Stenography.pdf (Size: 1.44 MB / Downloads: 88)
What’s steganography?
steganography
– embedding information (plaintext) within other
seemingly harmless information (covertext) in
such a way that no one but the intended recipient
would try to retrieve it
versus cryptography
– transforming information (plaintext) into other
unintelligible information (ciphertext) such that
no one but the intended recipient would be able
to retrieve it
Further differences
Steganography
- hide, without altering
– obfuscates the fact of communication, not the data
– preventative - deters attacks
Cryptography
– alter, without hiding
– obfuscates the data, not the fact of communication
– curative - defends attacks
Doing it with computers
Steganography – hiding a file inside of another
– typically hiding text inside of a media file
– normally used for the transportation of secretive
information
Operating System
– unused memory
slack space
unallocated space
– hidden partition
– normally used to hide data from investigators
Network
– unused bits in packet headers
– spread spectrum, frequency shifting
The protocols don’t restrict
IP “identification” field’s value
– “An internet header field carrying the identifying value assigned by the
sender to aid in assembling the fragments of a datagram.”
RFC 791, “Internet Protocol”
TCP “sequence number” field’s value
– “When new connections are created, an initial sequence number (ISN)
generator is employed which selects a new 32 bit ISN. The generator is
bound to a ... clock ... [but] not tied to a global clock in the network, and
TCPs may have different mechanisms for picking the ISN's.”
RFC 793, Transmission Control Protocol