Encrypt/Decrypt
Language used: VB script
It’s a simple code written in notepad, which can encrypt and decrypt text that can be sent as secret message. First line in the code creates a dialogue box that asks for a text to encode. Submitted text is then reversed. Next the %windir%\notepad opens up an instance of Notepad to print the results after waiting for 1 second. Then a function is written that encodes the text by advancing each character by 3 letters. Same procedure is followed in the decryption code. Only difference is at the function where it decodes the text by subtracting each character by 3 letters.
Block vs Stream Ciphers
•block ciphers process messages in blocks, each of which is then en/decrypted
•like a substitution on very big characters
–64-bits or more
•stream ciphers process messages a bit or byte at a time when en/decrypting
•many current ciphers are block ciphers
–better analysed
–broader range of applications
Block ciphers work a on block / word at a time, which is some number of bits. All of these bits have to be available before the block can be processed. Stream ciphers work on a bit or byte of the message at a time, hence process it as a “stream”. Block ciphers are currently better analysed, and seem to have a broader range of applicationsA block cipher is one in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length. Typically, a block size of 64 or 128 bits is used. As with a stream cipher, the two users share a symmetric encryption key. A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. In the ideal case, a one-time pad version of the Vernam cipher would be used ,in which the keystream (k ) is as long as the plaintext bit stream (p).
It’s a simple code written in notepad, which can encrypt and decrypt text that can be sent as secret message. First line in the code creates a dialogue box that asks for a text to encode. Submitted text is then reversed. Next the %windir%\notepad opens up an instance of Notepad to print the results after waiting for 1 second. Then a function is written that encodes the text by advancing each character by 3 letters. Same procedure is followed in the decryption code. Only difference is at the function where it decodes the text by subtracting each character by 3 letters.
Block vs Stream Ciphers
•block ciphers process messages in blocks, each of which is then en/decrypted
•like a substitution on very big characters
–64-bits or more
•stream ciphers process messages a bit or byte at a time when en/decrypting
•many current ciphers are block ciphers
–better analysed
–broader range of applications
Block ciphers work a on block / word at a time, which is some number of bits. All of these bits have to be available before the block can be processed. Stream ciphers work on a bit or byte of the message at a time, hence process it as a “stream”. Block ciphers are currently better analysed, and seem to have a broader range of applicationsA block cipher is one in which a block of plaintext is treated as a whole and used to produce a ciphertext block of equal length. Typically, a block size of 64 or 128 bits is used. As with a stream cipher, the two users share a symmetric encryption key. A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. In the ideal case, a one-time pad version of the Vernam cipher would be used ,in which the keystream (k ) is as long as the plaintext bit stream (p).