Asymmetric Encryption and it's Uses

"Public Key Crypto involves using 2 keys that are _________"

Mathematically related

Asymmetric Encryption in most cases is ______ times slower than Symmetric Encryption?

1000. Asymmetric Encryption is roughly 1000 times slower than Symmetric Encryption.

Public Key Crypto (Asymmetric)

A Cryptographic technique where both parties in the communication use different keys.

How does a digital signature process work?

Alice wants to ensure integrity so she encrypts with her Private Key, that message is then sent to Bob. From there Bob decrypts it with his Public Key. Anyone can decrypt the message, but we know for sure it's from Alice and nobody else. This is a digital signature.

Assymetric Encryption

Also known as Public Key Crypto, allows you to encrypt with one key and have slmeone else decrypt the message wity a different key.

Who can perform the Encryption?

Anyone can encrypt, the only thing you need to Encrypt is the Public Key.

Strengths and Weaknesses of Asymmetric Encryption:

Asymmetric Encryption is slow, but is great for sending messages to specific people.

What are the two uses of Public Key Crypto:

Confidentiality, and Integrity are the two uses of Public Key Crypto.

Asymmetric Encryption with a Public Key is meant for:

Confidentiality. No matter what Joe sends to Bob, only Bob can open that message.

"In Public Crypto there are 2 Keys, when you _____ with one you _______ with the other"

Encrypt, Decrypt

(T/F) "In Asymmetric Encryption you can only Encrypt with the Public Key that is known to the world"

FALSE. In Asymmetric Encryption you can Encrypt with the Public Key that is known to the world, OR you can Encrypt with the Private Key that is only know by the user. Whichever key you decide to Encrypt you must Decrypt with the other.

Public Key Crypto for Confidentiality:

If Alice wants to send a secret message, M, to Bob she computes the Cipher Text by Encrypting with Bobs Public Key, and he will then Decrypt it with his Private Key.

How secure is RSA?

If factoring large numbers is easy, RSA is easy to break. If factoring large numbers is hard, then RSA is hard to break.

Asymmetric Encryption with a Private Key is meant for:

Integrity. No matter what Bob sends to Joe, Joe will always know it legitimately came from Bob and nobody else.

Public and Private Keys? How do they work?

Public & Private keys in Asymmetric Encryption are Mathematically related keys that allow you to encrypt with one and decrypt with the other.

What was the first public key Crypto System:

RSA. The first public key crypto system was RSA.

The public is the product of two prime numbers

The private key is those two prime numbers

Would using just Public Key Encryption be a good idea for Big files?

No. Using Public Key Encryption solely for Big Files would be a horrible idea. Way too slow.

(-) Public Key Cryptography is very slow

AES-128 bit can be encrypted at 100MB/s......RSA-1024 is encrypted at 1MB/s

Real life example of Asymmetric, Public, Private Key Crypto:

If you rent a car, and go to return it and the office is closed. There is always a drop box for you to leave the keys. Only the manager has the keys to that drop box and will get your returned car keys the next morning. That is equivalent to Joe sending Bob are safe encrypted with his public key, and then only Bob being able to decrypt that message with his Private Key. Anybody can send Bob a message because they public key is public, but only Bob can decrypt the messages sent to him.

(T/F) "In RSA any bit size is acceptable"

TRUE. Unlike in AES and other Symmetric Crypto where you are limited to certain choices for block size and key size. In RSA any but bit size is acceptable.

Explain the process of a Bruteforce attack on RSA?

A Bruteforce attack on RSA is basically trying to factor the public key into two prime numbers. Which is hard and slow.

Explain a "Digital Signature"

A Digital Signature is not guaranteeing confidentiality but it is guaranteeing integrity.

Explain the Process of Asymmetric Encryption.

Bob generates two keys, a public key known the the world, and a private key only known to Bob. Alice sends Bob a message and Encrypts it with the Public Key, that is known the world. Bob receives the message and decrypts it with his Private Key which is only known by him. This is the process of asymmetric encryption.

What method of Encryption allows for both Confidentiality and Integrity:

Double-Encryption allows for both confidentiality and integrity.

Who can perform the Decryption of this secret message?

Only Bob, he is the only one with his private key therefor he is the only one who can decrypt the message.

In RSA asymmetric key crypto the prime number size is given in bits:

RSA - 2048 means RSA is using 2048- bit prime numbers to create the public and private keys. It has nothing to do with the key space.

Strengths and Weaknesses of Symmetric Encryption:

Symmetric encryption is fast but it isn't great at sharing keys.

(T/F) "There is no legit way to compare the nature of AES and RSA Encryption just based on key size"

TRUE. The key size numbers are measuring totally different things. It's not a useful comparison. Two totally different measurements.

What is the security of RSA based on?

The security of RSA is based on prime numbers and factoring

Speed problem for Integrity using Public Key Crypto:

What if you want to sign a large file? Public Key Crypto would be too slow. So instead you sign a Hash of the file. And send all of it to the other party.

In Symmetric Crypto the key size is given in bits:

AES - 128 means AES with a 128-bit key. 128-bits measures the key space, or the number of possible keys.

So is factoring large numbers easy or hard?

At this moment in time we have strong reason to believe factoring such long numbers is not an easy thing to do.

So we see how Alice Encrypted a secret message she wanted to send to Bob. How would Bob reply to Alice? Explain that process:

If Bob wants to reply he should encrypt that message with Alice's public key, the same way Alice sent the message to Bob.