Plain text:: meet me at next midnight. Thus to make it stronger, a double transposition was often used. This is simply a columnar transposition applied twice. The same key can be used for both transpositions, or two Fdifferent A keys N can C be used.
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Uploaded by veenadivyakish. Document Information click to expand document information Description: vcx. Did you find this document useful? Is this content inappropriate? Report this Document. Description: vcx. Flag for inappropriate content. Related titles. Carousel Previous Carousel Next. Jump to Page. Search inside document. Anonymous e6G8WLNe. Kingshuk Sinha. Solved AssignMents. Joby Paul. This system can also be used as a means for Bob to be sure a message comes from Alice.
If Alice wants to sign a message, she can encrypt it with her private key. When Bob receives an encrypted message which purports to be from Alice, he can obtain Alice's public key and decrypt the message. If a readable message emerges, Bob can have confidence that the message came from Alice, because Alice's public key would only properly unlock a message which was locked with her private key known only to Alice.
Figure-1 illustrates the public- key encryption process. This type of encryption has a number of advantages over traditional symmetric Ciphers. It means that the recipient can make their public key widely available- anyone wanting to send them a message uses the algorithm and the recipient's public key to do so.
An eavesdropper may have both the algorithm and the public key, but will still not be able to decrypt the message. Only the recipient, with the private key can decrypt the message. This makes it possible for Alice and Bob to simply send their public keys to one another, even if the channel they are using to do so is insecure. It is no problem that another person Eve now gets a copy of the public keys.
If Alice wants to send a secret message to Bob, she encrypts the message using Bob's public key. Bob then takes his private key to decrypt the message. Of course this means that Bob has to carefully guard his private key. With public key cryptography it is thus possible for two people who have never met to securely exchange messages. A disadvantage of public-key algorithm is that they are more computationally intensive than symmetric algorithms, and therefore encryption and decryption take longer.
This may not be significant for a short text message, but certainly is for bulk data encryption. Figure 1 : Public-Key Encryption [5]. Since that time, the algorithm has been employed in the most widely-used Internet electronic communications encryption program. Typical encryption techniques use mathematical operations to transform a message represented as a number or a series of numbers into a ciphertext.
Mathematical operations called one way functions are particularly suited to this task. A one way function is one which is comparatively easy to do in one direction but much harder to do in reverse. The RSA system uses one way functions of a more complex nature [7]. Specifically, the system uses modular arithmetic to transform a message into unreadable ciphertext.
Modular arithmetic is often called "clock" arithmetic, because addition, subtraction, and the like, work like telling time. This is because we subtract out 12 after doing the addition. Because the number 16 is "reduced" to the number 4 in the above example, one can say that "16 is reduced modulo The RSA system multiplies one number called the base by itself a number of times and the product is then divided by a modulus.
The number of times a base is multiplied by itself is called the exponent and the process is called modular exponent. So the plaintext M is regenerated using the formula, Cd mod n 4. New, faster and better methods for factoring numbers are constantly being devised. Obviously the longer a number is the harder is to factor, and so the better the security of RSA. As theory and computers improve, large and large keys will have to be used.
This will only become a problem if a new factoring technique emerges that requires keys of such lengths to be used that necessary key length increases much faster than the increasing average speed of computers utilizing the RSA algorithm.
RSA's future security relies solely on advances in factoring techniques. The individual steps are discussed in the following sub-sections. Speech Acquisition The recording of Bangla speech words was completed in a sound proof laboratory environment with the help of close-talking microphone, high quality sound card and sound recorder software.
The five hundred Bangla words originated from six speakers were recorded as wav file to make a sample database. The utterances were recorded at a sampling rate of 8. Pre-processing and Data Extraction To extract wave data, we first discard 58 bytes file header from the beginning of the wave file and then read wave data as character. The data extraction process extracts require voiced data from the input speech signal, which may contain silence, unvoice and voice.
This data are stored in a text file as integer data. This is usually done by detecting the proper start and end points of the speech events voicing and unvoicing and then separated into different pieces containing the audio signals on the basis of the detected start and end points [10], as shown in Figure Proper data extraction ensures better extraction of speech feature, which in turn results in better recognition accuracy.
The summary of the RSA algorithm is shown in the Figure Note that the factors p and q remain secret and n is public. Key Generation The system architecture for key generation is shown in Figure A random number generator generates bit pseudo random numbers and stores them in the rand FIFO. Once the FIFO is full, the random number generator stops working. The primality tester takes a random number as input and tests if it is a prime.
Modular Exponentiation The modular exponentiation operation is simply an exponentiation operation where modular multiplication is intensively performed. We implemented the bit and bit modular exponentiation components using LR binary method, where LR stands for the left-to-right scanning direction of the exponent. The pseudo code of the LR binary algorithm is given in the Figure In this research work, five hundred speech words were recorded from different speakers and were saved as.
To encrypt these speech words, at first we extracted integer data from the speech. The encryption program taken the txt file as input and performed encryption operation on the file to produce an unreadable encrypted message and saved another txt file. On the other hand, the decryption program taken the encrypted message file as input and performed decryption operation on the file to produce the original text file.
To generate the key pair, different values for p and q were tested. We selected 5 as the value of the encryption key e. Table-1 shows the encrypted and decrypted results of some speech words. RSA implements a public-key cryptosystem that allows secure communications and digital signatures, and its security rests in part on the difficulty of factoring large numbers. In this paper, an efficient implementation of RSA algorithm is used to encrypt and decrypt the speech data.
It must always be kept in mind that the integer representation of the message to be encrypted should lie within the range specified by the modulus i. Our further work will eliminate all the limitations of this algorithm and will implement the RSA digital signature scheme in speech communication systems.
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