ISC SSCP Exam Dumps Questions and Answers

It is the art and science of encoding hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message or could claim there is a message.

It is a form of security through obscurity.

The word steganography is of Greek origin and means "concealed writing." It combines the Greek words steganos (στεγανός), meaning "covered or protected," and graphei (γραφή) meaning "writing."

The first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book on magic. Generally, the hidden messages will appear to be (or be part of) something else: images, articles, shopping lists, or some other cover text. For example, the hidden message may be in invisible ink between the visible lines of a private letter.

The advantage of steganography over cryptography alone is that the intended secret message does not attract attention to itself as an object of scrutiny. Plainly visible encrypted messages, no matter how unbreakable, will arouse interest, and may in themselves be incriminating in countries where encryption is illegal. Thus, whereas cryptography is the practice of protecting the contents of a message alone, steganography is concerned with concealing the fact that a secret message is being sent, as well as concealing the contents of the message.

It is sometimes referred to as Hiding in Plain Sight. This image of trees blow contains in it another image of a cat using Steganography.

ADS Tree with Cat inside

This image below is hidden in the picture of the trees above:

Hidden Kitty

As explained here the image is hidden by removing all but the two least significant bits of each color component and subsequent normalization.

ABOUT MSF and LSF

One of the common method to perform steganography is by hiding bits within the Least Significant Bits of a media (LSB) or what is sometimes referred to as Slack Space. By modifying only the least significant bit, it is not possible to tell if there is an hidden message or not looking at the picture or the media. If you would change the Most Significant Bits (MSB) then it would be possible to view or detect the changes just by looking at the picture. A person can perceive only up to 6 bits of depth, bit that are changed past the first sixth bit of the color code would be undetectable to a human eye.

If we make use of a high quality digital picture, we could hide six bits of data within each of the pixel of the image. You have a color code for each pixel composed of a Red, Green, and Blue value. The color code is 3 sets of 8 bits each for each of the color. You could change the last two bit to hide your data. See below a color code for one pixel in binary format. The bits below are not real they are just example for illustration purpose:

RED GREEN BLUE

0101 0101 1100 1011 1110 0011

MSB LSB MSB LSB MSB LSB

Let's say that I would like to hide the letter A uppercase within the pixels of the picture. If we convert the letter "A" uppercase to a decimal value it would be number 65 within the ASCII table , in binary format the value 65 would translet to 01000001

You can break the 8 bits of character A uppercase in group of two bits as follow: 01 00 00 01

Using the pixel above we will hide those bits within the last two bits of each of the color as follow:

RED GREEN BLUE

0101 0101 1100 1000 1110 0000

MSB LSB MSB LSB MSB LSB

As you can see above, the last two bits of RED was already set to the proper value of 01, then we move to the GREEN value and we changed the last two bit from 11 to 00, and finally we changed the last two bits of blue to 00. One pixel allowed us to hide 6 bits of data. We would have to use another pixel to hide the remaining two bits.

The following answers are incorrect:

- ADS - Alternate Data Streams: This is almost correct but ADS is different from steganography in that ADS hides data in streams of communications or files while Steganography hides data in a single file.

- Encryption: This is almost correct but Steganography isn't exactly encryption as much as using space in a file to store another file.

- NTFS ADS: This is also almost correct in that you're hiding data where you have space to do so. NTFS, or New Technology File System common on Windows computers has a feature where you can hide files where they're not viewable under normal conditions. Tools are required to uncover the ADS-hidden files.

The following reference(s) was used to create this question:

The CCCure Security+ Holistic Tutorial at

and

Steganography tool

and

DES works with 64 bit blocks of text using a 64 bit key (with 8 bits used for parity, so the effective key length is 56 bits).

Some people are getting the Key Size and the Block Size mixed up. The block size is usually a specific length. For example DES uses block size of 64 bits which results in 64 bits of encrypted data for each block. AES uses a block size of 128 bits, the block size on AES can only be 128 as per the published standard FIPS-197.

A DES key consists of 64 binary digits ("0"s or "1"s) of which 56 bits are randomly generated and used directly by the algorithm. The other 8 bits, which are not used by the algorithm, may be used for error detection. The 8 error detecting bits are set to make the parity of each 8-bit byte of the key odd, i.e., there is an odd number of "1"s in each 8-bit byte1. Authorized users of encrypted computer data must have the key that was used to encipher the data in order to decrypt it.

IN CONTRAST WITH AES

The input and output for the AES algorithm each consist of sequences of 128 bits (digits with values of 0 or 1). These sequences will sometimes be referred to as blocks and the number of bits they contain will be referred to as their length. The Cipher Key for the AES algorithm is a sequence of 128, 192 or 256 bits. Other input, output and Cipher Key lengths are not permitted by this standard.

The Advanced Encryption Standard (AES) specifies the Rijndael algorithm, a symmetric block cipher that can process data blocks of 128 bits, using cipher keys with lengths of 128, 192, and 256 bits. Rijndael was designed to handle additional block sizes and key lengths, however they are not adopted in the AES standard.

The AES algorithm may be used with the three different key lengths indicated above, and therefore these different “flavors” may be referred to as “AES-128”, “AES-192”, and “AES-256”.

The other answers are not correct because:

"64 bits of data input results in 56 bits of encrypted output" is incorrect because while DES does work with 64 bit block input, it results in 64 bit blocks of encrypted output.

"128 bit key with 8 bits used for parity" is incorrect because DES does not ever use a 128 bit key.

"56 bits of data input results in 56 bits of encrypted output" is incorrect because DES always works with 64 bit blocks of input/output, not 56 bits.

Reference(s) used for this question:

Official ISC2 Guide to the CISSP CBK, Second Edition, page: 336-343

As session key is a symmetric key that is used to encrypt messages between two users. A session key is only good for one communication session between users.

For example , If Tanya has a symmetric key that she uses to encrypt messages between Lance and herself all the time , then this symmetric key would not be regenerated or changed. They would use the same key every time they communicated using encryption. However , using the same key repeatedly increases the chances of the key being captured and the secure communication being compromised. If , on the other hand , a new symmetric key were generated each time Lance and Tanya wanted to communicate , it would be used only during their dialog and then destroyed. if they wanted to communicate and hour later , a new session key would be created and shared.

The other answers are not correct because :

Public Key can be known to anyone.

Private Key must be known and used only by the owner.

Secret Keys are also called as Symmetric Keys, because this type of encryption relies on each user to keep the key a secret and properly protected.

REFERENCES:

SHON HARRIS , ALL IN ONE THIRD EDITION : Chapter 8 : Cryptography , Page : 619-620