Message hiding in audio file using variation of playfair cipher and audio steganography

Message hiding in audio file using variation of playfair cipher and audio steganography

Vimalanathan P (1), R Srividhya (2).

1M.Phil Scholars, SITS, Dr. G R D College of Science, Coimbatore.

2Assistant Professor, SITS, Dr. G R D College of Science, Coimbatore.

Abstract

Steganography is the method by which data or files can be hidden in Image files or any other type of file. Steganography is often confused with cryptography because the two are similar in the way that they both are used to protect confidential information. The difference between the two is in the appearance of the processed output. The output of steganography operation is not apparently visible but in cryptography the output is scrambled so that it can draw attention. This paper focuses on the strength of combining cryptography and steganography methods, variation of playfair cipher, 512 base conversion which results in enhancement of security.

Keywords – Image Steganography, Least Significant bit (LSB), Cryptography, Audio File Tag, secret Key, Playfair cipher

1. Introduction

   The objective of steganography is to hide a secret message within a cover-media in such a way that others cannot discern the presence of the hidden message. Technically in simple words steganography means hiding one piece of data within another. The word "Steganography" is of Greek origin and means "covered, or hidden writing. Modern steganography uses the opportunity of hiding information into digital multimedia files in the past people used hidden tattoos or invisible ink to convey steganographic content. Today, computer and network technologies provide easy-to-use communication channels for steganography. Steganography and Cryptography are great partners, in spite of functional difference. It is common practice to use cryptography with steganography. Naturally these techniques date back throughout history, the main applications being in couriering information during times of war. With the invention of digital audio and images files this has taken on a whole new meaning; creating new methods for performing reversible data hiding as it is often dubbed. This has many possible applications including the copyright watermarking of audio, video and still

   image data. In digital media, Steganography is mainly oriented around the undetectable transmission of one form of information within another.

   The embedded data must be undetectable within its carrier medium (the audio or image file used). The carrier should display no properties that flag it as suspicious whether it is to the human visual/auditory system or in increased file size for the carrier file. The embedded data must maintain its integrity within the carrier and should be easily removable, under the right circumstances, by the receiving party. The existing system of Audio Steganography poses more restrictions on the choosing of audio files. User can select only wav files to encode. Further embedding information into sound files is generally considered more difficult than images; However human ear is extremely sensitive to perturbations in sound and can in fact detect such turbulence as low as one part in 10 million.

2. Modern techniques of steganography

   The common modern technique of steganography exploits the property of the media itself to convey a message.

   • Plaintext

   • Image

   • Audio

   There are many techniques for hiding information or messages in audio in such a manner that the alterations made to the audio file are perceptually indiscemible. Common approaches Include.

   1. Least significant bit (LSB)

   2. Spread spectrum (SS)

   3. Parity coding

   4. Echo technique

   5. Noise Gate Technique

3. Proposed method

This paper proposes a novel method for secured data communication between 2 parties. When algorithm is adopted, user can send the file to other user then

receiver is able to retrieve the message from the send file. Thus, the data is protected without revealing the content to others. The system uses 4 layers of security in order to maintain data privacy.

Algorithm

Input: Message, Key, Audio File, Image 1 & Image 2

Output: Encrypted Message in Audio

Method:

1. Key is hidden inside an audio file using LSB method.

2. Message is encrypted based upon key which uses variation of playfair cipher.

determining whether the number is even or odd. The LSB is sometimes referred to as the right-most bit, due to the convention in positional notation of writing less significant digit further to the right. It is analogous to the least significant digit of a decimal integer, which is the digit in the ones (right-most) position.

Figure 2: Binary representation of decimal 149.

The binary representation of decimal 149, with the LSB highlighted. The MSB in an 8-bit binary number represents a value of 128 decimal. The LSB represents a value of 1. For example, to hide the letter "a" (ASCII code 97, which is 01100001) inside eight bytes of a cover, you can set the LSB of each byte like this:

10010010

3. The encrypted message is converted to 512 based	10011011
character set.	11010010
	10001010
4. The Encrypted message is hidden inside an image 1	00000010
and Image 2 using LSB. Image 1 and image 2 are	01110010

01010011

added to property of audio file.

Fig. 1

1. LSB coding

   A very popular methodology is the LSB (Least Significant Bit) algorithm, which replaces the least significant bit in some bytes of the cover file to hide a sequence of bytes containing the hidden data .In this paper, LSB method is used for hiding data. It is usually an effective technique in cases where the LSB substitution doesn't cause significant quality degradation, such as in 24-bit bitmaps. In computing, the least significant bit (LSB) is the bit position in a binary integer giving the units value, that is,

   00101011

   Fig.3

   The application decoding the cover reads the eight Least Significant Bits of those bytes to recreate the hidden bytethat is 0110001the letter "a." As you may realize, using this technique lets you hide a byte every eight bytes of the cover. Note that there is a fifty percent chance that the bit you're replacing is the same as its replacement, in other words, half the time, the bit

   doesn't change, which helps to minimize quality degradation. Fig.3 illustrates how the message 'HEY' is encoded in a 16-bit CD quality sample using the LSB method. Here the secret information is HEY and the cover file is audio file. HEY is to be embedded inside the audio file. First the secret information HEY and the audio file are converted into bit stream. The least significant column of the audio file is replaced by the bit stream of secret information HEY. The resulting file after embedding secret information HEY is called Stego-file.

2. Message Encryption using playfair cipher

   The Playfair cipher uses a 5 by 5 table containing a key word or phrase. Memorization of the keyword and 4 simple rules was all that was required to create the 5 by 5 table and use the cipher. To generate the key table, one would first fill in the spaces in the table with the letters of the keyword(dropping any duplicate letters), then fill the remaining spaces with the rest of the letters of the alphabet in order (usually omitting "Q" to reduce the alphabet to fit; other versions put both "I" and "J" in the same space). The key can be written in the top rows of the table, from left to right, or in some other pattern, such as a spiral beginning in the upper-left-hand corner and ending in the centre. The keyword together with the conventions for filling in the 5 by 5 table constitutes the cipher key.

   Fig. 4

   Mod % 5

   A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Z Y X W V U T S R Q P O N M L K J I H G F E D C B A

   X = [E J O T Y] Y = [V Q L G B]

   All character are considered (both in Ascending and descending) which are divisible by mod 5 are stored in an array x & y based on the position of letter in fig. 4 the alphabetic position is considered in x & y. this can be visualise as shown below.

   Fig 5

   The encrypted message usually occurs in pairs and the length of the encrypted message is twice the length of the original message. E.g. Consider the message JOB which has been encrypted each letter is searched in a table and its corresponding row and column values are retrieved.

   JOB = OV TQ JV

3. Conversion of encrypted message an 512 base character set

The encrypted message is converted into 512 base character set. ASCII characters can be split into the following sections.

0 31 Control codes

32-127 Standard, implementation-independent characters.

128-255 Special symbols, international character- generally, non standards characters.

512 base-character set

Control Codes: ASCII Characters 0 31

Decimal	Code	Description
000	NUL	Null
001	SOH	Start Of Heading
002	STX	Start of TeXt
003	ETX	End of TeXt
004	EOT	End Of Transmission
005	ENQ	ENQuiry
006	ACK	ACKnowledge.
007	BEL	BELl. Caused teletype
		machines to ring a bell.
		Causes a beep in many
		common terminals and
		terminal emulation
		programs.
Decimal	Code	Description
008	BS	Backspace. Moves the cursor

The following table lists and describes the first 32 ASCII characters, often referred to as control codes. The columns show the decimal and hexadecimal ASCII values for each code along with their abbreviated and full names. Descriptions are given to those most in use today.

032 033 034 035 036 037 038 039 040 041 042 043 044 045 046 047

Space ! " # $ % & ' ( ) * + , – . /

048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 064

0 1 2 3 4 5 6 7 8 9 : ; < = > ? @

		move backwards (left) one
		space.
009	HT	Horizontal Tab. Moves the
		cursor right to the next tab stop.
		The spacing of tab stops is
		dependent on the output device,
		but is often either 8 or 10
		characters wide.
010	LF	Line Feed. Moves the cursor to
		a new line. On Unix systems,
		moves to a new line AND all
		the way to the left.
011	VT	Vertical Tab.
012	FF	Form Feed. Advances paper to
		the top of the next page (if the
		output device is a printer).
013	CR	Carriage Return. Moves the
		cursor all the way to the left,
014	SO	Shift Out
015	SI	Shift In
016	DLF	Data Link Escape
017	DC1	Device Control 1
018	DC2	Device Control 2
019	DC3	Device Control 3
020	DC4	Device Control 4
021	NAK	Negative AcKnowledge
022	SYN	SYNchronous idle
023	ETB	End of Transmission Block
024	CAN	CANcel
025	EM	End of Medium
026	SUB	SUBstitute
027	ESC	ESCape
028	FS	File Separator
029	GS	Group Separator
030	RS	Record Separator
031	US	Unit Separator

The Standard ASCII Characters: 32 127

Decimal	Character	Decimal	Character
091	[	102	f g h i j k l m n o p
092	\	103
093	]	104
094	^	105
095	`_	106
096		107
097	a	108
098	b	109
099	c	110
100	d	111
101	e	112

ASCII Characters 32 – 127 are the standard, implementation-independent alphanumeric characters we work with every day. The tables below show the characters along with both their decimal and hexadecimal ASCII values.

Characters 32 – 64

The first table, which contains characters 32 – 64, contains the majority of the standard symbolic characters and the numbers from zero to nine.

Characters 65 127.

The second table, which contains characters 65 – 127, contains the standard Latin alphabet characters boh lower and upper case, separated only by a few characters at 91 – 96 and 123 127.

Decimal	Character	Decimal	Character
065 066 067 068 069 070 071 072 073 074 075 076 077	A B C D E F G H I J K L M	078 079 080 081 082 083 084 085 086 087 088 089 090	N O P Q R S T U V W X Y Z

Decimal

Character

Decimal

Character

Decimal

Character

Decimal

Character

113 114 115 116 117 118 119 120

q r s t u v w x

121 122 123 124 125 126 127

y z { | } ~ Delete

184 185 186 187

¸ ¹ º »

189 190 191

½ ¾ ¿

The Non-Standard ASCII Characters: 128 255. The second half of the ASCII table holds the non- standard extension set of characters which may vary depending which computer system you may be using. One common but in no way definitive example of this extended set is as follows.

Characters 128 191

Decimal	Character	Decimal	Character
128	· . · · · ' ' " · · ·	157
129		158	¡
130		159	¢
131		160	Non -breaking
132			space
133
134		161	¡
135
136		162	¢
137		163	£
138		164	¤
139		165	¥
140		166	¦
141		167	§
142		168	¨
143		169	©
144		170	ª
145		171	«
146		172	¬
147		173
148		174	®
149		175	¯
150		176	°
151		177	±
152		178	²
153		179	³
154		180	´
155		181	µ
156		182	¶

This first table contains characters 128 – 191, abstract symbols that appear in text from time to time.

Decimal	Character	Decimal	Character
192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223	À Á Â Ã Ä Å Æ Ç È É Ê Ë Ì Í Î Ï Ð Ñ Ò Ó Ô Ö Ö × Ø Ù Ú Û Ü Ý Þ ß	224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255	à á â ã ä å æ ç è é ê ë ì í î ï ð ñ ò ó ô õ ö ÷ ø ù ú û ü ý þ ÿ

The Non-Standard ASCII Characters: 256 512

This is based on Latin, Greek, Greek and Coptic, Extended Greek, Extended Latin, Cyrillic.

Characters 256-512.

Decimal	Character	Decimal	Character
183	·	188	¼

Decimal	Character	Decimal	Character
256 257 258	.	309 310 311

259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 302 303 304 305 306 307 308		312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360
Decimal	Character	Decimal	Character
361 362 363 364		413 414 415 416

365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412	.	417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464
Decimal	Character	Decimal	Character
465 466 467 468 469		489 490 491 492 493

470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488

494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512

E.g. Encryption using Playfair Cipher to encrypt i.e., consider the encrypted message OV TV JV, the corresponding message based on 512 base character set is 318,362,299,149,22

Consider a Message SYN

ASCII Value of Message is Convert the decimal value to Binary Value.

Values are

100111110

101101010

100101011

010010101

000010110

2 bit from LSB position of each pixel is modified by the binary values of encrypted message which results in Stegano Image. This Stegano image is added to the audio file as Back Cover. The Front cover of audio file is just image of 640 * 480 of Black Pixel. When the Audio File is played only the Black background image or Front Cover is displayed, but image is hidden in Back Cover.

4. Conclusion

In this paper, we have devoted a methodology of Embedding message in a audio file. In a second manner Image steganography is used for the transportation of high level or top secret documents between international governments. Also it allows for copyright protection on digital files using the message as a digital watermark. Image steganography has many legitimate uses as it can be used by hackers to send viruses and Trojans to compromise machines. Ensuring data security is a big challenge for computer users. In this paper, the proposed method for embedding message in image, and in turn the image is embedded in audio file as cover media. The Algorithm will not work efficiently; if keywords contain repeated alphabets. A meaningful keyword may contain at most 17 distinct characters. Variation for the algorithm can be discovered, so it works with repeated character.

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[3]. An Enhanced and Secure Playfair Cipher by Introducing the Ferquency of Letters in any Plain text, Journal of Current Computer Science and Technology, 1 (3), June 2011, 10-16.

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