Crypto FAQ: What is cryptography? What is encryption?
This Cryptocurrency FAQ consists of Frequently Asked Questions related to cryptography ("crypto") and encryption technologies and their practical applications.
For a general overview of cryptography and the practical application of encryption techniques to cryptocurrencies, see the following FAQs:
- Alt. Phrasing: What is cryptology?; What is a encryption/decryption?
- Defn: cryptography
[noun]
Cryptography is the study and practice of secure communication techniques that allow only the sender of a message to code (cipher, or encrypt) a message so that only the intended receiver of the message can decode (decipher, or decrypt) and view its semantic contents. Cryptographic techniques assume the presence of adversarial third parties who seek to intercept and decrypt (decode or decipher) the secure encrypted (coded or ciphered) messages for nefarious purposes. In general practice, cryptography is concerned about designing and analyzing secure communication protocols that thwart adversaries from intercepting and decrypting messages.
Cryptographic techniques tend to be multi-disciplinary, as they encompasses various branches of mathematics (algebra, probability, statistics, game theory), computer science (algorithms, complexity theory), electrical engineering (hardware design, FPGA, ASICs), digital signal processing (DSP), physics, and others.
Common applications of cryptography include computer passwords, ATM cards, smart credit cards, cryptocurrencies, electronic commerce transactions, and military communications.
Usage Semantics: The term cryptography is sometimes conflated with the term cryptology, where the former is the practical application of secure communication techniques, whereas the latter is the formal study of these techniques.
Strong cryptography refers to cryptographic techniques based on industry-tested standard algorithms that use robust encryption key lengths. At the time of this writing, examples of industry-tested standards algorithms for minimum encryption strength include AES (128 bits and higher), TDES (minimum triple-length keys), RSA (2048 bits and higher), ECC (160 bits and higher), and ElGamal (2048 bits and higher).
Compare: cryptology
Contrast: plaintext (cleartext)
References:
* Understanding Cryptography: A Textbook for Students and Practitioners, C. Paar et al., 2010.
- Defn: cryptocurrency
[portmanteau: noun "crypto(graphy)" + noun "currency"]
Cryptocurrency is a decentralized form of digital currency that uses strong cryptography techniques (e.g., blockchains with cryptographic hash functions) and distributed peer-to-peer networks to securely regulate currency generation and fund transfers independent of central banks.
For a more comprehensive explanation of cryptocurrency, see the source FAQ: What is cryptocurrency and how does it work? on fhe CryptoCurrencyWorks.com web.
For a general overview of cryptography and the practical application of encryption techniques to cryptocurrencies, see the following FAQs:
Decryption is the inverse process of encryption, in which encoded messages, referred to as ciphertext, are decoded into plaintext, so that their original unencrypted content may be read.
To explicate further, consider the following pseudocode for the complementary cryptographic algorithm functions encode and decode with parameters plaintext, cryptokey, and ciphertext:
encode (plaintext: String; cryptokey: String): ciphertext: Stringdecode (ciphertext: String; cryptokey: String): plaintext: String
The input and output parameters for encode and decode functions are described below:
- plaintext: the unencrypted message or other information which is an input parameter to the encode function, and is a return parameter for the decode function.
- cryptokey: the cryptographic key used by both the encode and decode functions to encrypt and decrypt the plaintext and ciphertext parameters respectively. Note that the cryptokey need not be identical for both encryption and decryption.
- ciphertext: the encrypted message or other information which is a return parameter for the encode function, and is an input parameter for the decode function.
In addition to encryption and decryption algorithms, cryptographic keys can be used for other cryptographic algorithms, such as digital signature schemes and message authentication codes.
Public-key encryption is an asymmetrical cryptographic system which uses a pair of mathematically related cryptographic keys:
- public key: As its name implies, the public cryptographic key is widely known. Public keys are typically made available via a public directory or repository.
- private key: As its name implies, the private cryptographic key is confidential, and is closely held by the message recipient or information concealor.
The cryptographic key pair is mathematically related in the sense that whatever is encrypted via a public key can only be decrypted via a private key, and vice versa. For example, if Alice wants to send a confidential message to Bob, and wants to ensure that only Bob can read it, Alice can encrypt the message with Bob's public key. Only Bob, or someone with access to his corresponding private key, will be capable of decrypting the encrypted message back into its original unencrypted form. Even if someone intercepts Bob's encrypted message druing transmission, its contents will remain confidential if the interceptor lacks access to Bob's private key, which is essential for decryption.
To explicate further, consider the following pseudocode for the complementary cryptographic algorithm functions encode and decode with parameters plaintext, ciphertext, publickey, and privatekey, where the last two parameters represent a complementary public-private cryptographic key pair:
encode (plaintext: String; publickey: String): ciphertext: Stringdecode (ciphertext: String; privatekey: String): plaintext: String
The input and output parameters for encode and decode functions are described below:
- plaintext: the unencrypted message or other information which is an input parameter to the encode function, and is a return parameter for the decode function;
- ciphertext: the encrypted message or other information which is a return parameter for the encode function, and is an input parameter for the decode function.
- publickey: the public cryptographic key used by encode as an input parameter to encrypt the plaintext input parameter.
- privatekey: the private cryptographic key used by decode as an input parameter to decrypt the ciphertext input parameters.
In the context of security in general, and cybersecurity in particular, authentication is the act of confirming of the truth of an attribute of a single piece of data (a datum) claimed true by an entity. There are several levels of security authentication:
- Single-Factor Authentication (SFA), where you need to provide at least one kind of credential, typically something that you know (see below), to authenticate;
- Two-Factor Authentication (2FA), where you need to provide two out of three kinds of credentials to authenticate.
- Three-Factor Authentication (3FA), where you need to provide three out of three kinds of credentials to authenticate.
- Something that you know, such as a password, a Personal Identification Number (PIN), or a geometric pattern.
- Something that you have, such as an ATM card, credit card, mobile phone, or fob.
- Something that you are, such as a biometric id (e.g., fingerprint, voiceprint, iris scan).
Theory vs. Practice: The theoretical basis for the soundness of zero-based privacy algorithms is based on rigorous cryptographic methods for zero-knowledge proofs. The practical applications for zero-based privacy algorithms include secure file synchronization and sharing and secure email systems. In the case of secure file synchronization and sharing systems, the client’s seeks to securely store plain-text data on a server so that the data can be shared and data updates synchronized across multiple distributed devices (e.g., desktop, notebook, tablet, smart phone). As long as the client encrypts its plain-text data before it uploads via a secure communication protocol (e.g., IPS/TLS) it relative straightforward to implement zero-knowledge privacy between the data server. (Note: that even though many file synchronization and sharing vendors claim “end-to-end encryption” of data they fall short of zero-knowledge privacy because they don’t ensure that client data is encrypted before it is uploaded to their servers.)
Note that the difficulty of implementing zero-knowledge privacy is significantly increased when the client seeks to securely share data with a third party. Although it is relatively well understood how to resolve this problem using recursive design techniques, a further discussion of theoretical and practical solutions to the third-party sharing problem is outside the scope of this FAQ. (Contact us if you seek further information about this advanced topic.)
Cryptoeconomics is a cross-disciplinary approach to the study of digital economies and decentralized finance (DeFi) applications. In addition to traditional economic concepts and principles (production, distribution, and consumption of goods and services), cryptoeconomics synergistically integrates concepts and principles from cryptography, computer science, and mathematical game theory disciplines.
— [Source: FAQ: What is cryptoeconomics and how does it work?]
For a more comprehensive explanation of cryptoeconomics see the source FAQ: What is cryptoeconomics and how does it work? on fhe CryptoEconWorks.com web.
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