(Very) Basic Intro to PGP (GPG)

computer with encrypted data on screen

The post (Very) Basic Intro to PGP (GPG) appeared first on Qvault.

PGP, or its open-source alternative, GPG, is a program used to encrypt data such that only an authorized party can decrypt it. In this introduction, we will cover its use-cases and a high-level overview of the algorithms involved.

Both programs (and others) adhere to the OpenPGP protocol. Because it is an implementation agnostic protocol, people can use the software they are most comfortable with and still send secure messages to each other.

Only Pretty Good?

The “pretty good” part of “Pretty Good Privacy” is a hilarious understatement. It uses secure building blocks and remains an extremely private (albeit not very user-friendly) protocol for secure communication.

Symmetric vs Asymmetric Encryption

Asymmetric algorithms allows users to communicate securely without sharing private keys. They are suitable for the encryption of messages meant to be sent over an untrusted medium like emails or text messages.

Symmetric algorithms are computationally fast. They are primarily used to encrypt data at rest, such as files on a hard drive.

Asymmetric vs Symmetric encryption pgp

PGP is a hybrid cryptosystem, it takes advantage of certain benefits from symmetric and asymmetric systems. PGP uses asymmetric keys to encrypt symmetric keys, which are used to encrypt messages. This keeps PGP computationally efficient while also allowing users to own their own private keys.

How Does It Work?

OpenPGP, the protocol to which PGP and GPG adhere, can really be looked at as a set of rules for how we use other encryption and authentication algorithms. There are four main components of a PGP system:

Putting It All Together

Let’s go through each step of how a PGP message exchange works:

  1. Raw data is hashed and signed using the sender’s asymmetric private key. This will allow the receiver to verify that the message is from who they think it is.
  2. The data is compressed in order to save space
  3. A new random symmetric key is generated for this exchange
  4. The random symmetric key is used to encrypt the compressed data
  5. The symmetric key is encrypted using the receiver’s asymmetric public key
  6. The encrypted symmetric key and the encrypted data are sent to the receiver
  7. The receiver uses their private key to decrypt the symmetric key
  8. The receiver uses the symmetric key to decrypt the data
  9. The data is decompressed
  10. The receiver verifies the digital signature using the sender’s public key
PGP Step by Step flowchart

That’s it! If you have questions be sure to reach out on Twitter.

Which Algorithms are Used?

PGP defines in the official RFC 4880 which algorithms must and should be supported by PGP clients. Let’s go over each one.

Symmetric Encryption Algorithms:

Implementations MUST implement TripleDES.

Implementations SHOULD implement AES-128 and CAST5.

Implementations that interoperate with PGP 2.6 or earlier need to support IDEA, as that is the only symmetric cipher those versions use. Implementations MAY implement any other algorithm.

https://tools.ietf.org/html/rfc4880#section-9.2

Asymmetric Encryption Algorithms:

Implementations MUST implement DS for signatures, and Elgamal for encryption.

Implementations SHOULD implement RSA keys.

RSA Encrypt-Only and RSA Sign-Only are deprecated and SHOULD NOT be generated but may be interpreted.

See section 13.8 for notes on Elliptic Curve, ECDSA, Elgamal Encrypt or Sign, and X9.42.

Implementations MAY implement any other algorithm.

https://tools.ietf.org/html/rfc4880#section-9.1

Digital Signature Algorithms:

Implementations MUST implement SHA-1. Implementations MAY implement other algorithms. MD5 is deprecated.

https://tools.ietf.org/html/rfc4880#section-9.4

Compression Algorithms:

Implementations MUST implement uncompressed data. Implementations SHOULD implement ZIP. Implementations MAY implement and other algorithm.

https://tools.ietf.org/html/rfc4880#section-9.3

Thanks For Reading!

Follow us on Twitter @q_vault if you have any questions or comments

Take game-like coding courses on Qvault Classroom

Subscribe to our Newsletter for more educational articles

The post (Very) Basic Intro to PGP (GPG) appeared first on Qvault.



source https://qvault.io/2020/07/27/very-basic-intro-to-pgp-gpg/

Comments

Post a Comment

Popular posts from this blog

Why is Exclusive Or (XOR) Important in Cryptography?

Image
If you are getting into cryptography, or just trying to understand the fundamentals, you may have noticed that the exclusive-or operation is used quite often, especially in ciphers. What is XOR ( ⊕ )? XOR, or “exclusive or” operates on binary data. It returns true if both of its inputs are opposites (one false and one true), otherwise, it returns false. An example in go code would be something like: func exclusiveOr(a bool, b bool) bool { return a != b } XOR Cipher – The Perfect Cipher The XOR operation can be used as a simple cipher for encrypting and decrypting messages with a single key. This is known as symmetric encryption. It is interesting to note that if: The key is the same size as the message The key is kept secret and generated truly randomly Then the cipher is impossible to crack. This is known as a one time pad . However, a simple XOR shouldn’t be used in production due to the key length needing to be too long to be practical. Cipher Example A...
Read more

Base64 vs Base58 Encoding

Image
By Lane Wagner –  @wagslane  on Twitter Base64 is one of the most popular encoding formats for representing data. Have some binary data? Base64 encode it for convenient readability and parsing. Base58 is just another encoding format (with 58 characters instead of 64, and has gained popularity largely due to Bitcoin and other cryptocurrencies. When it comes to data encoding, there is typically a trade-off made between: Human Readability: Do humans have a good idea of what is being represented at a glance? Efficient data compression: How many bytes are used to represent the same data? Let’s rank Base58, Base64, and ASCII encoding against each other using these metrics! First: A Note on Binary All data is stored in a raw binary format on computers. These encoding formats (Base64, Base58, and ASCII) are just different ways of reading and writing binary data. For example, in Base64 the binary code 000000 represents the letter A , but in ASCII the binary 00000000 repres...
Read more

(Very) Basic Intro to Hash Functions (SHA-256, MD-5, etc)

Image
This is going to be a basic introduction to hash functions. I will assume most of my audience is here to gain an understanding of why hash functions are used and the basic idea of why they work. My goal is to explain it in a general sense, I will be omitting proofs and implementation details and instead focusing on the high-level principles. Why Use A Hash Function? Hash functions are used all over the internet in order to securely store passwords, find duplicate records, quickly store and retrieve data, and more. For example,  Qvault  uses hashes to extend master passwords into private encryption keys. A longer list of uses here:  https://en.wikipedia.org/wiki/Hash_function#Uses I want to focus on several important features of hash functions, arguably the most important features. Hash functions scramble data deterministically No matter the input, the output of a hash function always has the same size The original data can not be retrieved from the scrambled d...
Read more