Recommended
More Related Content
Similar to Basic Cryptography & Security
Similar to Basic Cryptography & Security (20)
More from Hoffman Lab
More from Hoffman Lab (20)
Recently uploaded
Recently uploaded (20)
Basic Cryptography & Security
- 1. Basic Cryptography & Security Eric Roberts Hoffman Lab
- 2. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication ● Cryptographic terminology ● Public keys and passwords ● Evaluating your personal security Motivation
- 3. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: XYZABCDEFGHIJKLMNOPQRSTUVW Plain Text: “Hoffman Lab!” Cipher Text: “Elccjxk Ixy!” Creating Secrets
- 4. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Plain Text: “11110000” Key: “01010101” Cipher text: “10100101” Cipher: Exclusive OR (XOR) ● Switch if ‘1’ in the key Creating Digital Secrets
- 5. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Cipher text: “10100101” Key: “01010101” Plain Text: “11110000” One Time Pad ● Use the key only once Revealing Digital Secrets
- 6. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication ● What about a 2 TB secret? Key Problems Block Ciphers Stream Ciphers (Triple) DES - 56 bit key RC4 - 40 to 256 bit keys AES (Rijndael) - 128/192/256 bit keys Salsa20 - 256 bit keys
- 7. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication PuTTY example
- 8. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication VIM example (don’t use) :set cryptmethod=”blowfish2” ● Doesn’t provide any message authentication ○ Easy to temper with ● Easy to brute force decipher Don’t try to implement your own encryption - even published standards. Use libraries. Block cipher https://github.com/vim/vim/issues/638
- 9. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Key principles ● Key length: ○ Age of the universe: ■ 4.36 x 1026 ns ○ 256 bit key: ■ 1.15 x 1077 possibilities ● Re-using keys makes them less secure
- 10. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Asymmetric keys “Hello!” Encrypt My Public Key “Hello!” Decrypt My Private Key Transfer Anyone who wishes to send me a private message: Me as the receiver: ● Different keys are used for encrypting and decrypting
- 11. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Creating a public key (ssh) $ ssh-keygen usage: ssh-keygen [-q] [-b bits] [-t dsa | ecdsa | ed25519 | rsa | rsa1] [-N new_passphrase] [-C comment] [-f output_keyfile] $ ssh-keygen -t ed25519 Generating public/private ed25519 key pair. ... Your identification has been saved in /users/eroberts/.ssh/id_ed25519. Your public key has been saved in /users/eroberts/.ssh/id_ed25519.pub. ● ed25519 is recommended currently however it may not be available on older servers ● Otherwise: “ssh-keygen -t rsa -b 4096 -a 100 -o”
- 12. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Sharing your public key $ ssh-copy-id mordor
- 13. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Secure your private keys This should not be possible: $ ssh -i /users/cviner/.ssh/id_rsa mordor Trustico - SSL certificate reseller Never trust any service that produces a private / public key on your behalf Washington Post article on TSA keys
- 14. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication ● Technically keys ● Key Derivation Functions ○ MD5 ○ PBKDF ○ bcrypt ○ scrypt Passwords
- 15. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication * https://www.tarsnap.com/scrypt/scrypt-slides.pdf (From 2009)
- 16. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication From horrible to less horrible: 1. Stored as plain text 2. Run through a hash function 3. Run through a hash function with a salt Bad Password Storage
- 17. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Hashing (Passwords) Data (or password) as large as you want Unique 256-bit number Hash function (SHA-256) ● Same input always produces the same output ● No known two inputs to produce the same output for SHA-256 ● Shattered.io ● Passwords and rainbow tables ● Salt is public and avoids fights rainbow tables Salt (unique gibberish) Example: 98c0f87ec38b0c86817cfa9dc9d894a3468b611048f45060729509505d4543b 5
- 18. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password DBs Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Bad Password databases Username Hashed Password Mickael c616027b32758d9220a0e6b91899b2c1a06f521381fd6ac222 c6fda6a3ace6ec Rachel 531eb382d6274e9cad931b209a359842d6c79022b35361ec5 c9c4c1afc559d71 Mehran c616027b32758d9220a0e6b91899b2c1a06f521381fd6ac222 c6fda6a3ace6ec ● Weak password = look up in a table ● Password leaked for Mickeal = Password leaked for Mehran Bad Network Database
- 19. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Better Password DBs Username Hashed Password Salt (public!) Mickael 8d3dcedf007d016be15a3016 b60711d6146d1107e62229fc ff503bc6f97b2649 b95093mvf89s8a Rachel c80b21d4a843f38f00b33cde 9634171d602779fbdb65a273 108bb09ecc439df8 b9t0p94jhlf980qf083 Mehran 69a0168e9d9a180b43ebf237 09cb96dff2173f5ed430f2136 5b5e57a52623ab9 9b08v23r8yfeh3791bj
- 20. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication ● LinkedIn (2012) - unsalted SHA-1 ● Evernote (2013) - unsalted MD5 ● Yahoo (2013) - (unsalted?) MD5 ● NCIX (3 weeks ago) ○ (unsalted?) MD5 ○ Credit card info in plaintext ● Toronto and Region Conservation Authority (2017 - present?) ○ Plain Text * haveibeenpwned.com (look yourself up) Password Mismanagement
- 21. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication ● Use a Password Manager ○ 1Password ○ LastPass ○ KeyPass ● Only have to remember 1 very strong password ● Not perfect Password Management
- 22. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Auth 1. Knowledge (Password) 2. Possession (Device) 3. Inherence (Fingerprint) Multi-factor Authentication ● Use two of these factors when possible
- 23. Crypto and Security Motivation Creating Secrets Creating Digital Secrets Revealing Digital Secrets Key Problems PuTTy example VIM example (don’t use) Key Principles Asymmetric Keys Creating a public key Sharing a public key Secure your private keys Passwords KDF relative strength Bad Password Storage Hashing (Passwords) Bad Password Databases Better Password DBs Passwd Mismanagement Password Management Multi-factor Authentication Questions? Cryptographic Right Answers: https://latacora.micro.blog/2018/04/03/cryptographic-right-answers.html
Editor's Notes
- The point of this presentation is to arm yourself with at least a broad-strokes understanding of keeping your data and yourself secure at any computer you use. There is an awful lot of jargon when it comes to Cryptography and we’ll go over what I think is believed to be the most relevant and will give you enough context to make your own educated decisions and understand programs you use better (like SSH, e-mail, your web browser). Passwords are hazardous and everyone, but not everyone in this lab, should be using public/private keys when it comes to use on Bitbucket or logging into other machines. And ideally armed with all of this information everyone should be able to make more conscious decisions about evaluating security of your own and other systems
- The idea of secretly storing or transmitting messages is nothing new. Here we have the quitenessential Ceaser Cipher. The letters are moved back 3 letters in their respective alphabet. In cryptograhic terms the original message is called “Plain text” while the encrypted message is called “Cipher text”. This was actually used by Ceaser evidentally. No you should not use it.
- In the world of computing, our infomation is stored binary digits or bits so we have to come up with methods of encrypting (and decrypting) information in this format. Even in digital formats, information is universally still referred to as plain text. Here we’re introducing a “key” which “locks” or encrypts a message. The idea is if you see a “1” in the key, you switch the corresponding bit in the plain text to produce the following cyphertext. Exclusive OR is likely the most important cypher in crytographic history. The NSA called it "perhaps one of the most important in the history of cryptography."
- To decrypt, use the same key and the same rule as before the get the “plain text” back! This cipher is called a One Time Pad. It is actually perfectly secure if you can trust the source. It’s not had to imagine if you had only the cipher text and no key, your best bet to get at the plain text is to only guess. Each bit “flips” whether or not there is a corresponding 1 in the key. If the key is truly hidden your stuck unless you guess at every possible key. It’s called a one time pad since, in this case, the key should only be used once. If you use it repeatedly, say on characters of an e-mail, you suddenly give a would be secret stealer more information and hints as to what the original key is (by say counting repeated occurances of a cyphertext and assuming the top pick is likely the letter ‘e’, etc).
- No one uses the one time pad. One of the most glaring problems is if someone wants to send 2 TB of data secretly, you’d have to come up with a 2 TB key first (and somehow mutually and securely decide on it before hand). Practically ciphers are used with a key that is *much* shorter than than the given text is used to encrypt data. Most ciphers, but not all, use XOR significantly in their constructions. Ciphers typically work on chunks of data whether that’s in a stream of bits or a blocks. I’ve given some popular examples below. It’s not important to really know how they work only that there are a lot of them and recognizing when you might be using an insecure or out-of-date one. These names will come up every once in a while. These ciphers are far more common than you think even though you don’t see their names too often. AES, for example, has worked into the instruction set of intel-based processors since 2008.2 Never ever try to create your own cipher. Older ones are likely to be insecure. RC4 and (not triple) DES should be avoided if at all possible.
- So you’re thinking when would ever care to know about these ciphers? Here you can actually select or disallow ciphers. Maybe not practical in some cases - but very useful to know in case someone has, for example, checked that box for use of single-DES.
- Here’s a good example of why you should be wary about other people implementing ciphers. VIM has a rather forgetting cryptmethod option. Don’t use it. It’s bad by all security standards. Neovim, a popular fork of VIM, removed this option entirely.
- For creating and using keys bigger is better. As to some context as to why even a 256 bit key is usually good enough is to show how large the possible number of keys there are compared to say - the lifetime of the universe in nanoseconds. If you had a computer running since the dawn of time guessing at your secret 256 bit key, chances are you’re still very safe. Notably on average, a guesser only needs to guess half of the possibilites before arriving at the answer. Grover’s algorithm? As mentioned before key re-use is bad since it continually gives out information about the cipher text however so slight. If you wonder why some websites suddenly become “insecure” - it’s because their key has “expired” and is considered no longer secure enough. So they need to create a new one or the update has yet to be reflected on your computer.
- There are forms of cryptography where the same key is not used for both encrypting and decrypting data. This is incredibly useful since it means if I want to have secure communication with any stranger all I have to do is provide a public key where I secretly keep my corresponding private key. This is like providing an open lockbox or safe to a stranger and keeping the key. They could put their message inside, mail or deliver it, and only you could open it.
- It’s very easy to create. The -t option allows you to choose the algorithm or type of public/private key you wish to generate. RSA and DSA are old and not as secure as the ecdsa or ed25519. These algorithms refer to elliptic curves, or specifically the “ec” portion. RSA stands for Rivest–Shamir–Adleman. Here I generated an an elliptic curve public/private key pair and kept the defaults (256 bits and 16 iterations). It’s more secure than a 4096 bit key for RSA. The program importantly tells you where your private and public keys are stored. Your private key *must* stay private.
- This is how you copy your public key to mordor. Now if you don’t have a passphrase attached to your key - you can login without a password. The computer you login in from, after adding your key, is implictly trusted unless you specify otherwise. On bitbucket you have to copy your public key manually. The public key from the file given by ssh-keygen. After this presentation I’m removing the password option from pushing the website script. Just put a key on bitbucket and be significantly happier for yourself please.
- I should not be able to login using someone else’s ID. This should be the default though if you’ve accidentally granted read access to your entire home directory then you’re in a bit of trouble. Other real examples of bad private key sharing include the Washington post providing a very hi-res photo of the TSA master keys. These were prompted produced into 3d printable versions (that work) Back in March (of 2018), a SSL certificate reseller, a service that certifies your public key, claimed that a bunch of their keys they had been compromised. They proved this fact by e-mailing out over 50000 private keys. How they got the private keys is questionable and why they decided to e-mail them out is also questionable.
- Passwords can act like keys (in real life) For secure use digitally, they are transformed by a key derivation function which takes a text password, and produces a key that is unique to that user. This is in the best case and you can only at best trust that the service storing your password is actually doing this.
- These attacks timings are a decade old (read much faster now) and are against the *best possible case* someone has done the right thing by storing your password.
- Passwords can act like keys (in real life) For secure use digitally, they are transformed by a key derivation function which takes a text password, and produces a key that is unique to that user. This is in the best case and you can only at best trust that the service storing your password is actually doing this.
- SHA-1 has been proven to be broken as of 2017 (A forged PDF with the same resulting hash) It’s possible to download freely produced tables of all combinations of say all 10 numbers and letters and see what their resulting hash is for a given function. If a would be attacker gets a hold of your only just-hashed password that is relatively short (< 10 characters) they can just look it up in a database.
- In case it isn’t blindly obvious - never share passwords across sites.
- A password manager is a program that stores your passwords in a single secure repository. It can generate passwords and ensure you do not have repeated passwords across devices, websites, etc. It seems like a bad idea to have a single point of failure. “Password managers don't have to be perfect, they just have to be better than not having one”
- In the world of authentication there are 3 types of evidence you can provide. Most commonly the device is your phone. Though there are other devices that specialize in, say, storing a private key such as Yubikey
- Lots of topics I did not address such as Message Authentication Codes, Side-channel attacks, Sources of randomness (for key generation), etc. I’m by all means not an expert on these topics and I’d wager that there is probably only a very small number of people in the world who are. In general stick to recommendations, audited implementations, and avoid doing this stuff on your own. If you google Cryptographic Right Answers there’s been a long evolving-over-the-years discussion of what the recommended go-to for particular applications are required. Hopefully after a brief overview from this presentation you should be able to make better sense of the discussion invovled.