Hey there! With cyberattacks constantly in the news these days, cryptography has been on my mind quite a bit. Cryptography refers to the science and mathematical techniques for securing communications and information systems. I thought it would be helpful to provide an overview and explanation of the main forms of cryptography in use, how they work, and some examples of their application in the real world.
There are three essential categories that all modern cryptographic algorithms and protocols fall into:
- Symmetric key cryptography
- Cryptographic hash functions
- Asymmetric (public key) cryptography
I‘ll explore each one in detail. But first, let‘s summarize the overall purpose and goals of cryptography technology which sets the stage:
Cryptography 101
At the highest level, cryptographic systems aim to provide the following critical security properties:
- Confidentiality: Keeping data private and unreadable to unauthorized parties
- Integrity: Preventing improper modification of data
- Authentication: Verifying identities and origins of messages/entities
- Non-repudiation: Ensuring senders cannot deny sending a message
Now the mechanisms typically employed to achieve these goals include:
- Encryption algorithms: Scramble plaintext data into ciphertext only decipherable with keys
- Hash functions: Output fixed length digests/fingerprints that detect data changes
- Digital signatures: Bind messages to sender identities using math
- Key establishment: Securely agree on keys for subsequent encryption
So in summary, the major objectives here are to keep sensitive information hidden and immune to being maliciously altered while also reliably verifying where messages came from.
Equipped with a high-level overview, let‘s get into the nitty gritty math magic! We‘ll start with symmetric encryption…
Symmetric Key Cryptography: Simple and Fast
Symmetric algorithms, sometimes called secret key algorithms, use a single key to both encrypt and decrypt data. This key needs to remain private and so must be securely transmitted ahead of time to intended recipients in order for them to decrypt messages.
The advantages of symmetric cryptography include speed and low computational demands. Encryption and decryption with these ciphers is fast even for data sets in the gigabyte range. The functions themselves are based on relatively simple math and logic operations.
Some weaknesses however include scalability with multiple users and efficient secure delivery of keys between communicators. Special strategies need to be devised for these issues which add complexity.
Let‘s look closer at exactly how symmetric encryption schemes operate…
Symmetric Crypto Step-by-Step
Alice wants to send sensitive financial data to Bob over the public internet. For privacy protection, symmetric encryption will be used to secure the transmission as follows:
- Pre-Shared Key Setup: Alice and Bob agree on using AES-256 encryption, generating a shared 256-bit key over an end-to-end encrypted channel
- Encryption: The plaintext financial data is encrypted by Alice using the AES-256 algorithm initialized with the pre-shared secret key
- Exchange: The resulting ciphertext is sent from Alice to Bob across the public internet
- Decryption: Upon receipt of the ciphertext, Bob decrypts it using AES-256 with the same key, reproducing the original plaintext data
Provided the secret key remains exclusive to Alice and Bob, this process allows confidential transmission even over insecure networks like the internet where data could potentially be intercepted. The secret key effectively unlocks access to read the data.
Symmetric cryptography forms the basis for a broad range of essential security technologies we rely on daily for things like…
- Encrypted messaging (Signal, WhatsApp, iMessage)
- Secure file storage (VeraCrypt containers)
- Website traffic protection (TLS/SSL, VPN tunnels)
- Whole disk encryption (BitLocker, FileVault)
- Cryptocurrencies (protecting wallet private keys)
So in many ways it powers confidentiality assurances in this digital age. Next let‘s explore cryptographic hash functions!
Cryptographic Hash Functions: Digital Fingerprints
While symmetric algorithms focus directly on keeping data private, hash functions serve a different crucial role.
Hash functions take input data of variable lengths like documents, messages, files and deterministically produce an output fixed length digest or fingerprint. This output hash uniquely represents the input data like a fingerprint. Some examples you may have heard of are MD5, SHA-1 and SHA-256.
Key attributes that make cryptographic hashes so useful:
- Deterministic – Same inputs = Same digests
- Quick to calculate – Even for data gigabytes in size
- Infeasible to reverse – Impossible to determine original input from hashes
- Avalanche effect – Small input changes cause drastic digest changes
These qualities allow hash functions to efficiently verify data integrity and detect malicious tampering or transmission errors. If an altered copy of data produces different hash digests than the original, modifications are revealed.
Hash functions accomplish these feats by employing clever cryptographic mixing and digest generation algorithms designed precisely for extreme sensitivity to message contents. Let‘s examine the four phases:
Behind the Scenes – How Hash Algorithms Work
- Message Preprocessing: Techniques like padding are applied to strengthen against shortcuts
- Message Parsing: Entire message is divided into fixed length blocks
- Compression Function: Processes each block, outputting interim digest values
- Output Processing: Final passes mix digests into the hash fingerprint
By combining multiple rounds of substitution, transposition, modular math, and bit shifting, hash functions result in digests exhibiting avalanche effects. Attempting to reconstruct the original input becomes hopeless.
Now what does this provide in practical terms? Main applications of cryptographic hashes include:
- File integrity verification
- Secure password storage
- Message authentication codes (MACs)
- Random number generation
- Digital signatures
Hash functions facilitate integral security capabilities we rely on constantly today including error detection, identity management, trusted communications, and more.
Up next we‘ll transition to public key cryptography which presents an alternative approach…
Asymmetric Cryptography: Enhanced Security with Key Pairs
Symmetric ciphers require securely pre-sharing secret keys somehow. To remove this nuisance while retaining confidentiality guarantees, a clever invention called public key cryptography emerged in the 1970s.
Also referred to as asymmetric cryptography, this flavor uses key pairs – one public and one private. Data encrypted by a public key can only be decrypted by its corresponding private key. The private key uniquely unlocks messages locked by its public counterpart.
Benefits over conventional secret key encryption include:
- Removes pre-shared key distribution headaches
- Enables strong authentication via public keys
- Provides non-repudiation via binding messages and sender identities
Tradeoffs encompass slower speeds and high computational overhead, but computers have mostly caught up in performance capabilities.
Now let‘s examine the encryption process step-by-step:
Asymmetric Encryption Walkthrough
- Alice and Bob each create public-private key pairs using reliable encryption software
- Alice obtains a copy of Bob‘s public key
- To send Bob an encrypted message, Alice uses his public key to transform the plaintext into ciphertext
- Alice sends the encrypted result to Bob through any medium
- Upon receipt, Bob decrypts the ciphertext using his private key, reproducing Alice‘s original plaintext
Seamless and elegant! Public keys only need to be openly accessible rather than transmitting secret keys. Properly implemented, data encrypted by public keys has uncrackable protections, even against unforeseen future attacks.
Under the hood, advanced mathematical techniques form the foundations for the one-way nature of public key crypto operations. Algorithms like RSA rely on factoring extremely large prime numbers while Elliptic Curve methods use properties of elliptic curve equations over finite fields.
Let‘s discuss some real world application areas that asymmetric cryptography enables…
Where Public Key Encryption Keeps Us Secure
- Secure web traffic (HTTPS and SSL/TLS protocols)
- User authentication in systems
- Software and document digital signatures
- End-to-end encrypted messaging
- Cryptocurrency wallets
Overall this flavor supercharges security in many spheres. The sealed and certified delivery of messages combined with strong identity verification take confidentiality into a new era.
Cryptography Type Comparison
| Category | Symmetric Key | Hash Functions | Asymmetric Key |
|---|---|---|---|
| Also Called | Secret key encryption | Cryptographic hash, digest, fingerprint | Public key encryption |
| Key Mechanism | Single key for encryption & decryption | Not explicitly key-based | Public-private key pairs |
| Strengths | Speed, computational efficiency | Verify integrity, fast unique digests | Enhanced security, non-repudiation, authentication |
| Weaknesses | Scalability, key distribution | Non-encryption capability | Slower, resource intensive |
| Use Cases | Bulk encryption, databases, real-time apps | Passwords, file integrity, random numbers | Web security, signatures, user identity |
In Closing…
I aimed to provide an understandable overview of the three families of cryptographic algorithms actively safeguarding systems and secrets in the digital realm. Symmetric ciphers quickly scramble bulk data. Hash functions enable verification and screening. Asymmetric methods facilitate identity and authentication assurances.
Of course entire university courses and careers center around tightly focused aspects of cryptography. But hopefully this beginner introduction shines some light on the magical mathematical foundations subtly protecting everyday experiences online! Please let me know if you have any other questions!
