CS50 Cybersecurity - Lecture 1 - Securing Data

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This is CS50, Harvard University's introduction to the intellectual enterprises of computer science and the art of programming.

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TABLE OF CONTENTS

00:00:00 - Introduction
00:00:17 - Securing Data
00:02:21 - Hashing
00:39:52 - Secret-Key Cryptography
01:03:21 - Public-Key Cryptography
01:16:14 - Digital Signatures
01:27:57 - Passkeys
01:34:47 - Encryption in Transit
01:40:10 - Deletion
01:46:28 - Encryption at Rest
01:50:59 - Ransomware
01:52:24 - Quantum Computing

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LICENSE

CC BY-NC-SA 4.0
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License

David J. Malan

[leksandradubovik]

Damn. I watched CS50 with younger David when I began Bachelor in Cybesecurity. Now I am writing my masters and still watching CS50. This quality of teaching will never bore me!

[avadhpatel]

They are changing the game with the high quality and easy to understand courses

[bidyashankarojha_]

Being Harvard student, i can assure u all that quality and purity of knowledge is fabulous both online and offline

[leksandradubovik]

Explaining Quantum Cryptography in just 3 Minutes, what a genius! Even my non-IT friendly friends were really intrestet to listen to this

[abstraction]

Wow! What a great lecture full of details. With CS50, I am starting or already started to love computer science more than ever. Thanks alot for the CS50 team. Much appreciation!

[cndoblast]

"Alllright...THIS is CS50!..." always makes me goosebumps.

[leocrypto]

How good are these courses to provide you the basis of a subject in an understandable way. Thank you!

[SA_GAMER]

Thanks for giving free access on youtube and edex platform

[MahmoodHasand]

Amazing it’s what I have been waiting for

[jeimohwash-kern]

Wow, i started cyber security with lesson 0 of this and i was able to decode the statement OR FHER...using a simple C program to be sure to mean, , its actually of great help, , , i mostly lve the teacher.

[EsquireR]

Cryptography is actually the trickiest thing to wrap my mind around, like multiple keys for locking/unlocking publicity/privacy...

[Justin.]

My dream is to know what makes me active, and cs50 is one

[tdpfrrt]

31:31 WHAT if it uses auto completions and cache to check for autocompletion and if true enumerates this? Also sso and a sys admin resetting the pass and with permission has a prefered pass set could send from here; Especially with prompted to change passwd. Probably more of an IntraNet feature perhaps but i don't think makes the company poorly.

38:38 this means that if the adversary can go through bucket would know how many sets of hashes each bucket has and from 100 out of 10 groups only has 8 unique hashes?

55:46 is this why chatgpt hallucinates and how image generations are trained?

58:19 cant you just make the password filter and user account control to alarm when censored.

59:13 but do the mathematician discuss the salt and matching pairs variable?


1:11:59 26 might throw zerodivision error? since mod is false ** mod != mod / True

1:15:23 But rotational ciphr would be the correct choice since at this layer you either decrypted the hash thus far or have abstraction scoped.

1:15:30 You mean that there are ascii and hex2dec similar that nuance salt:hashing pair values.

1:18:19 an unescaped, escaped reference to string literal symbol || ```PS2

[yiannisserpico]

A. If salt value is chosen by moment on time, is there still a possibility any salting value be same as another one? Since any time moment is never same as another one. I believe if hashing function has in it a moment time variable, then it is impossible two or more salting values be the same. But, again, my assumption is based on the fact that hashing function has time variable (is base on time moments). B. 37:20 Are you refered to hash tables? Thank you professor.

[yiannisserpico]

On salting method, why do the output characters include salting value? Why is it necessary? b. If hashing function takes for two password+salting (same password but two different salting), the output will normally be different without being necessary to have on beginning of two outputs the salting value, unless on software code it is fixed, but I do not find a reason why. Thank you!

[Ewakaa]

I thought the salt will preferably be the row number
Love how he respects Hackers

[saiadwith]

i didnt understand rainbow tables, can anyone explain?

[yiannisserpico]

Sir, where is the hashing function been stored? I guess somewhere on the server. Isn't there a possibility/danger for a hacker to find it there? Unless it is not stored on servers. But if not, where? Thank you!

[aleksandardimov]

In regards to the salting technique, given that a username on a website must me unique, isn’t it better to use that as salt, in order to guarantee that there will be no two equal hash values stored in the database? With the addition that to really guarantee uniqueness of the hash value its fixed-length must be of the same length as the max allowed length of the username and password combined.

[moltyfoam]

If my public key can decrypt the message or value i send on the server and since the key is available to almost everyone doesn't that make me vulnerable to an attack?? I dont get it