Algorithms and Milkshakes

Created Tuesday 22 February 2022

FROM THIS

To THIS


(and back?)

Milkshake Model

(Incidentally)

Source Code -> Binary

Milkshake Model

DELIBERATELY

Encryption and Hashing.

Milkshake Model

Encryption - Hard to turn back

Milkshake Model

Hashing - *Impossible* to turn back, more later

Dan Brown

(wrote a dumb book)

Unbreakable Encryption Probably Still Exists

Yep, even given all the NSA stuff. You have to be super careful

(all breaking you see is usually "backdoors"

not fundamentals)

Encryption

The basic tools for encryption are mostly available to all…

...even if the social factors, companies, corporations, and governments aren’t down.

(remember, you gotta have it on BOTH SIDES)

Old School Encryption

Caesar Cipher. (yes, this really used to fool people)

DWWDFN WKH HDVW ZLQJ RI WKH IRUW DW WKUHH RQ WKXUVGDB..

you got it

attack the east wing of the fort at three on thursday

Quick aside: Another thing

What about hiding the message ITSELF?

Shave a guy's head ... and wait?

Steganography

Hiding the fact that the message (or payload) exists at all

Examples:
- fake personal ad to say something else
- having a safe but hiding valuables in a shoebox
- weird bits in a jpg

History of Hidden Messages

Languages, dialects, patois'...

CULTURAL ENCRYPTION.

CULTURAL AUTONOMY.

(ever heard of “code switching?”)

Recap

Steganography v. Encryption

Steganography

Examples:
- fake personal ad to say something else
- having a safe but hiding valuables in a shoebox
- weird bits in a jpg

Steganography

Useful, but imperfect, esp online
Bad, because: Robots and radio

Better..

Why YES, you can have a copy.

OF JUNK! TOO BAD YOU CANT READ IT!

(This is Encryption)

Encryption: Sending VERIFIABLE secrets

ALICE needs to send a verifiable message to BOB
but CAROL is trying to listen in.

“This is a conversation between A and B so you can C your way out!”

Some definitions:

CLEARTEXT - (should be obvious)
CIPHER - The system of encryption
CIPHERTEXT - the (hopefully not-understandable) gibberish generated
KEY - the arbitrary decoding or encoding "key/password-ish thing" - sometimes not both.

More strategy

Secret METHOD
vs
Public METHOD, secret KEY

Why not interrogate the creators?

Some standard ideas

Security through obscurity* is generally a bad idea:

*The STRICT definition, meaning
"Relying on secrecy in implementation or design,
NOT in the key"

Security through obscurity

"Any person can invent a security system so clever that she or he can't think of how to break it."
Schneier's Law

(you can generalize this to a lot of things; e.g. Open Source, Auditing, etc)

Never roll your own

(Or better yet, do, and throw it out. You'll learn something)

Better

New Strategy, if you can meet

The bookstore strategy

OR

The One-Time Pad 

	  but what if you CAN'T meet each other...

But, we are usually "strangers"

  1. Public (asymmetric) Key Encryption
  2. Diffie Hellman Key Exchange.

Whats Mathy and Milkshakey?

What, even for a computer, is VERY FAST in one direction..

..and IMPOSSIBLY SLOW in the other?

(remembering,
all computers do is math?

Hey, remember factoring?

24
4 * 6
2 * 2 * 2 *3?

What about 17?

What about 17?

PRIME

It's MATH all the way down

One Way Strategies.

So we use this for KEY encryption

Phil Zimmerman

Invents this. "Hey, this is pretty good privacy!"

Eben Moglen

"Cool idea, no cap. Also, when the FBI kicks down your door, holla"

One weird flipside of this:

Who's MORE powerful than the government?

Gotta sign checks and credit cards!

Encryption and Signatures

Encryption and digital signatures are two sides of the same coin.

You need digital signatures to send money, so we also have encryption. (mostly)

Let's slow down because this is amazing

Because wait: If it's just me and you, its like we just met.

But if it's
Amazon ,Buyer and Card thief..?
and we want to keep this on going.

No seriously. Remember my "mesh" from 2 weeks ago?

If ALL THE SIGNALS ARE IN THE AIR
and MY COMPUTER or PHONE HAS TO SEE ALL OF THEM

Why can't I just steal the password the first time you send it?

What if I do this dirtiness

I invite you to my house,
where I have COMPLETE CONTROL of my router.
I get you to buy something from Amazon for the first time ever
HOW DO I NOT STEAL YOUR CREDIT CARD?
I'm watching LITERALLY ALL OF THE TRAFFIC?

DIFFIE HELLMAN

(pretend that you can't "unmix" colors. Milkshake)

Also — Passwords

When you lose your password, what does the website do?

Make you change it?

Or

Send you a copy of it.

If they're nice enough to send you your password?

If they're nice enough to send you your password?

THEY SUCK AT SECURITY.

Good websites will NOT send you your password.

Because they don't actually know it.

Encrypted passwords, right?

...kinda.
One way to do this:

1) Get their password
2) Save it on your computer
3) Then, encrypt it for safety.

What do we really need?

The actual password

or

simply:
Proof that they typed in the same thing both times?

What do we really need?

Remember: “encrypting” something always yields:

GIBBERISH

“MyPassword123” > ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab

What do we really need?

Remember: “encrypting” something always yields:

UNIQUE GIBBERISH

“MyPassword123” > ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab
means that
”DifferentPassword456” ≠ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab

So NEVER save the password,

just the gibberish!

NOT
“MyPassword123” = “MyPassword123”

BUT

“ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab”
=
“ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab”?

And “MyPassword123” IS NOT ON THE SERVER

Wait, do we need alladis?

“ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab”
=
“ab18db351a3ed3849cca9839d98381ee6392eeb391baa39d766290082812d9eceab”?

Try this

“ab18db351a3”= “ab18db351a3”*

As long as
we use ALL the data in the original to get this number
And it’s STILL mathematically unliklely that two different passwords will yield the same short gibberish, we’re good to go.
(not exactly this)

A dumber, similar thing

Presumption: The network (or person) is imperfect. The bytes we receive may not always be the exact ones that were sent.

Also: The network or verification is “slow”

We need a shorter, but verifiable, version of the data.

Hashing

Error checking/Checksumming.
One tiny change in the original still means BIG changes in the gibberish.

(MD5, which is fast, but not super-secure) is good for this)

Hashing

Error Checking/Checksums
Password “Storage”
Bitcoin/Cryptocurrencies

Passwords

They don't store your password (your secret ingredient)

They just store the entire milkshake....and calculate/mix it every time.

(don't use MD5, use something deliberately slow, like bcrypt)

To beat up some more analogies

Consider your mom’s _______ recipe?
(milkshake?)

Even if you don’t know the ingredients..
… you know when it’s WRONG :)

More details on Hashing

Horrible – storing the password

Better but still bad – storing the password hashed

Decent – storing “userid+password” hashed

Best – storing “userid+password+salt” hashed

Process

Login: jmarks
password: g00dpassword
(salt): b00gab00ga
jmarks+g00dpassword+b00gab00ga
==HASHED==>
02f39aae85ad73e162b446e918597e89