How Does SHA-1 Work - Intro to Cryptographic Hash Functions and SHA-1

SHA-1 stands for Secure Hash Algorithm 1, a cryptographic hash function developed by the NSA that can be used to verify that a file has been unaltered. In this video, we go over the basic features and common implementations of cryptographic hash functions before diving into the inner workings of a Javascript implementation of the SHA-1 function. Although out of use now, walking through the hash function code provides valuable insight into how these algorithms work.

Watch this video to learn:

- What are Cryptographic Hash Functions
- Practical uses for Cryptographic Hash Functions
- How does SHA-1 work

[ruchamathure]

This was so helpful! I have to give a presentation (which I totally forgot about till today) on SHA-1 to my entire uni class & professor tomorrow and didn't know anything about it, but this video was so comprehensive, even to the uninitiated that I feel quite confident now!

[NghtRder]

initialize some variables... umm wat? what happened to explain things? in-fact after this point the whole explanation went out the window for most following steps

[johnnydabz]

Best I've seen so far. Nice work.

[madfangkills]

Definitely loved you walking through the algorithm. It's so much better breaking it down into understandable chunks

[machinelearningid]

Thanks, this is most concise explanation in the youtube

[kareemsharawi]

It truly was a "great presentation Sam" :-) Thanks a lot!

[DoctorSantosh]

Too bad the most important part (step 11) didn't contain any detailed information other than the sentence "a bunch of xor". Thanks God we have the screenshot of his code !

[bryandussanjimenez]

Wo, this is what I was looking for a long time, appreciate your job, thanks

[TheCTMcG]

I didn't follow your reasoning on the 448 aspect of 512 mod 448. shouldn't it be <length> mod 512 == 0 ?

[adrianpilikser]

Although the video is really helpful and explains everything in great detail, I have to add that the shown h and k values are fundamentally different to those used in practice, thus producing completely different results.
But otherwise it is a wonderful lesson dives deep in the workings of the SHA1 algorithm.

[starkxz]

Thanks Sam. That was really a great presentation 👍🏻

[zNeoDev]

I don't get the step 11 in how sha-1 works :/

[wilsonbalderrama]

amazing this explanation is the best one I've seen, kudos to the presenter

[tymothylim]

Thank you very much for this video! Really interesting and educational! :)

[manipal]

In Hashing (encryption is done but decryption is not possible)

[alejandroamoros]

Wow what a great video and a great explanation. I understand the steps you are taking but I am missing a lot of knowledge to understand what is going on. Whats should I know before fully comprehending SHA functions? Should I learn binary/bit wise operations/programming? I'll rewatch a couple of times but as a noob to this, I think this is too advanced for me yet. What can I learn to make this easier to understand? Thanks!

[omarshoura]

So I don’t know if I’m understanding it wrong but the purpose of a hash function might be to verify that a message hasn’t been corrupted.
That is down by hashing the message then sending the hash result along with it and the way the receiver checks it is by hashing the message and see if it matches?
Ok then so how come a hacker won’t just also change the hash output so that it seems like nothing has been hacked.
And if you check it against the hash that the sender stored then in sending that hash to the receiver to verify it, couldn’t a hacker change that too?
Please explain this to me.

[fmartin]

There's a siren sound in the video.

I thought it was from windows lol

[Strasbourgeois]

9:14 what's the reason of adding 1 at step 4

[darkzero]

At Step 7: it is 64 Bits as you show 64 bit padding zeros in front.
Step 8: Do we need to append to 64 bit to binary msg 512 bit(both msg + array length 64bit) or
step 5 is already 512 bit and added 64 bit length gives 512+ 64 = 578.
Which one is correct? Confused!