1 00:00:08,370 --> 00:00:12,850 Let us start with the news section overview of cryptography. 2 00:00:13,740 --> 00:00:20,490 In this video, I'm going to give you a general overview, an introduction to what is cryptography? 3 00:00:21,240 --> 00:00:24,440 Cryptography is the practice and study of hiding information. 4 00:00:25,380 --> 00:00:29,970 It is sometimes called code, but this is not a really correct name. 5 00:00:31,270 --> 00:00:38,260 It is the science used to try to keep information secret and safe, modern cryptography is a mix of 6 00:00:38,260 --> 00:00:41,470 mathematics, computer science and electrical engineering. 7 00:00:42,100 --> 00:00:47,900 Cryptography is used in ATM cards, computer passwords and even shopping on the Internet. 8 00:00:48,610 --> 00:00:55,120 It is a matter of storing and transmitting data in a particular form so that only those for whom it 9 00:00:55,120 --> 00:00:57,190 is intended can read and processing. 10 00:00:57,730 --> 00:01:04,690 Cryptography not only protects data from theft or attrition, but can also be used for user authentication. 11 00:01:05,620 --> 00:01:12,070 This process is called encryption and has been used for centuries to prevent handwritten messages from 12 00:01:12,070 --> 00:01:12,700 being read. 13 00:01:12,700 --> 00:01:18,770 But unintended response to the cryptography is used to protect digital data. 14 00:01:19,690 --> 00:01:26,110 It is a division of computer science that focuses on transforming data into formats that cannot be recognized 15 00:01:26,110 --> 00:01:27,580 by unauthorized users. 16 00:01:28,720 --> 00:01:35,950 An example of basic cryptography is an encrypted message in which letters are replaced with other characters. 17 00:01:36,490 --> 00:01:44,290 To decode the encrypted contents, you will need a grid of tables, basically incident and the suffix 18 00:01:44,440 --> 00:01:48,130 graffy stands for writing in computer science. 19 00:01:48,370 --> 00:01:54,940 Cryptography refers to secure information and communication techniques derived from mathematical concepts 20 00:01:55,090 --> 00:01:58,840 and a set of rule based calculations called algorithms. 21 00:02:00,570 --> 00:02:06,810 These deterministic algorithms are used for cryptographically generation digital signing verification 22 00:02:06,810 --> 00:02:12,780 to protect data privacy, web browsing on Internet and confidential communications such as credit card 23 00:02:12,780 --> 00:02:14,100 transactions and email. 24 00:02:14,730 --> 00:02:21,330 Cryptography is probably the most important aspect of communications security and is becoming increasingly 25 00:02:21,330 --> 00:02:24,680 important as a basic building block for computer security. 26 00:02:25,380 --> 00:02:32,310 Modern cryptography concerns itself with the four objectives confidentiality, integrity and repudiation 27 00:02:32,310 --> 00:02:33,330 and authentication. 28 00:02:34,020 --> 00:02:37,530 Let us have a look at Sir William Starling's conventional model. 29 00:02:38,190 --> 00:02:45,150 Cryptography involves two phrases encryption and decryption, and encryption is the process through 30 00:02:45,150 --> 00:02:48,690 which one can convert the plain text into encoded text. 31 00:02:49,020 --> 00:02:50,370 Let's call it the ciphertext. 32 00:02:50,490 --> 00:02:52,440 By using encryption algorithms. 33 00:02:52,860 --> 00:02:54,570 These algorithms are public. 34 00:02:55,560 --> 00:03:01,530 This ciphertext is then decoded into plain text through decryption by using decryption algorithms. 35 00:03:02,570 --> 00:03:08,060 But more data is needed to be transmitted from one end to another, the same, the kind words plaintext 36 00:03:08,060 --> 00:03:13,790 in the ciphertext, the receiver, upon receiving this ciphertext, decoded into plain text. 37 00:03:14,240 --> 00:03:20,900 By doing this, no third party can get access to the message and even he or she gets the message that 38 00:03:20,900 --> 00:03:26,990 it is not possible to decode until and unless they have access to the keys in this whole process of 39 00:03:26,990 --> 00:03:32,420 encoding and decoding what the party uses either same or different keys in their algorithms. 40 00:03:32,840 --> 00:03:36,140 Well, here's the simplest way to understand cryptography. 41 00:03:36,860 --> 00:03:42,320 Imagine you're sending someone a letter in the mail, but you only want the person you're sending it 42 00:03:42,320 --> 00:03:43,190 to read the message. 43 00:03:43,790 --> 00:03:50,510 Maybe you're sending something private and you want make sure that no one looks inside the message with 44 00:03:50,510 --> 00:03:51,250 cryptography. 45 00:03:51,610 --> 00:03:56,630 Imagine spreading the letter into a hundred pieces before you send it, and then once it gets to the 46 00:03:56,630 --> 00:03:59,780 desired recipient, it automatically reassembled itself. 47 00:04:00,350 --> 00:04:06,770 The only difference is that with cryptography, it's more like you are sharing 10 billion pieces. 48 00:04:08,030 --> 00:04:13,280 Perhaps the most advanced cryptography in the ancient world was achieved by the Romans. 49 00:04:13,970 --> 00:04:20,030 A prominent example of Roman cryptography known as Caesar Cipher involves shifting the letters of an 50 00:04:20,030 --> 00:04:24,280 encrypted messaging by a certain number of places down the Latin alphabet. 51 00:04:24,890 --> 00:04:29,930 Knowing this system and a number of places to send the letters, a recipient could successfully decode 52 00:04:30,110 --> 00:04:33,660 otherwise illegible message in the next lecture. 53 00:04:33,890 --> 00:04:36,320 We are going to see symmetric encryption.