
A comprehensive guide to private key encryption
Private key encryption is one of two primary methods organizations use to conceal sensitive data and enable secure communication. Not sure how it works? Read on and learn everything you need to know, including how it differs from public key encryption, its primary use cases, and more.
What is private key encryption?
Private key encryption, also known as symmetric encryption or private key cryptography, is an encryption method that uses a single key to encrypt and decrypt data. The cryptographic key must be kept secret and shared only between the parties involved in the communication to ensure confidentiality — hence why it’s also called a “secret key.”
This is the opposite of public key cryptography, which uses a different key for encryption and decryption.
What is encryption?
According to the National Institute of Standards and Technology (NIST), encryption is the cryptographic transformation of plaintext into ciphertext using an algorithm. In simpler terms, it’s a process that obfuscates data’s original meaning to prevent it from being known or used. The reversal process is called decryption, which transforms the encrypted data (or encrypted message) back into readable plaintext.
Although often used interchangeably, encryption and cryptography are similar but different terms. NIST defines the latter as the science of information hiding and verification. It’s a discipline that embodies the principles, means, and methods of rendering sensitive information unintelligible and restoring encrypted data to intelligible form.
In short, encryption is one of those methods. The essential difference that sets it apart is that it uses algorithms to conceal sensitive data mathematically.
Why is encryption important?
Broadly, encryption is vital for a few significant reasons:
- Confidentiality: Public and private key encryption methods protect sensitive information from unauthorized access. Without the corresponding private key, an encrypted message is unreadable to anyone who gets their hands on it. Even if a hacker intercepts or steals the data, it may be of no use to them if they can’t crack the encryption.
- Integrity: Encryption also sees that data isn’t altered during transmission or storage. Encryption mechanisms often include cryptographic hashes, which generate a unique fingerprint for the data. Any change to the original encrypted data — no matter how minor — will result in a mismatched hash during verification, alerting users to potential tampering.
- Authentication: Encryption establishes secure communication by verifying the identity of the sender or receiver through mechanisms like digital signatures and cryptographic keys. For example, in email communication, encryption can authenticate the sender, ensuring that the message truly came from the stated individual or organization.
- Compliance: It can also help organizations meet regulatory requirements for data security, especially in industries like finance, healthcare, and government. For instance, in the United States, the Health Insurance Portability and Accountability Act (HIPAA) requires organizations to encrypt data at rest to protect sensitive health information. Violations can result in monetary penalties, lawsuits, and reputational damage.
Private key encryption use cases
There are many potential applications where private key cryptography can prove valuable. Some of the most common include:
File or data encryption
Private key encryption is essential for safeguarding sensitive files stored on devices or servers, ensuring that only authorized individuals can access their contents. By encrypting files with a symmetric key, businesses can protect confidential information such as financial records, contracts, or intellectual property from unauthorized access, even if a device or server is compromised. Moreover, private key encryption enables secure file sharing within organizations, allowing employees to collaborate safely while minimizing the risk of data breaches.
Database security
Databases often store vast amounts of sensitive customer data, such as personal details, payment information, and transaction histories, making them prime targets for cyberattacks. Private key encryption ensures this data remains protected, even in the event of a breach.
By encrypting data at rest, organizations can render the information unreadable to unauthorized users, preserving its confidentiality and integrity. Additionally, private key encryption is critical for securing backup databases, ensuring stored copies remain protected from misuse. For industries reliant on trust, such as e-commerce and banking, database encryption builds confidence by safeguarding customer information against unauthorized access.
Secure communication
Private key cryptography is fundamental to securing websites and enabling safe online communication, primarily through the use of Transport Layer Security (TLS) certificates.
When a user visits a website protected with Hypertext Transfer Protocol Secure (HTTPS), a process called the TLS handshake occurs. This establishes a secure connection by negotiating encryption parameters between the user's browser and the web server. Initially, asymmetric encryption is used to exchange a symmetric session key.
Once this cryptographic key is securely created, symmetric encryption takes over for the duration of the session, encrypting the data exchanged between the client and server. This ensures that sensitive information, such as login credentials, payment details, and personal data, is protected from eavesdropping or tampering by unauthorized parties.
Additionally, it authenticates the website’s identity, helping users confirm that they are interacting with a legitimate site and not a phishing page or spoofed version. This is particularly critical for e-commerce platforms, online banking, and any site handling sensitive customer interactions, as it builds trust and protects users against fraud.
Disk encryption
Organizations use private key encryption to secure entire storage devices, such as hard drives, USB drives, or external SSDs. This ensures that all data stored on the device remains encrypted and inaccessible to unauthorized users without the proper decryption key.
Disk encryption is particularly useful for protecting lost or stolen devices, ensuring that sensitive information cannot be extracted even if the physical hardware falls into the wrong hands. Enterprises often rely on disk encryption for laptops and portable devices used by employees, helping to maintain security in a mobile workforce.
What’s the difference between public and private key encryption?
Both public and private key methods are widely used, but there are notable differences between them. Let’s take a closer look at each individually to understand their advantages and limitations.
Public key encryption
Public key encryption — also known as asymmetric encryption or public key cryptography — doesn’t use just one cryptographic key to encrypt and decrypt data. Instead, it uses a key pair: a public key (available to anyone) and a private key (kept secret to the owner).
The key pair is mathematically linked. That means data encrypted with the public key can only be decrypted with the corresponding private key, and vice versa.
Its advantages include:
- Simpler key distribution: In public key cryptography, organizations only need to keep the private key secret. They can share the public key openly without compromising security.
- Greater security: The key exchange process is much more secure in public key encryption since the secret key is never shared.
- Scalability: This encryption method is highly scalable because the public key can be freely distributed, making it ideal for multi-party communication.
However, there are a few notable disadvantages:
- Speed: Asymmetric encryption typically involves greater computational complexity, resulting in slower encryption and decryption processes.
- Resource intensity: Generating and managing a public-private key pair for every user in large-scale systems adds administrative overhead.
- Key management: Managing a key pair for each user can become complex in systems with a large number of people.
Due to these factors, public key encryption is well-suited for digital signatures and scenarios requiring robust authentication and security. However, it may not be ideal for bulk data encryption or high-speed applications.
Private key encryption
As a symmetric encryption method, private key cryptography offers several advantages:
- Greater simplicity: With just one single key for both encryption and decryption, the process is generally much faster and more straightforward than asymmetric cryptography.
- Efficiency: Likewise, it’s less computationally complex, making it ideal for encrypting large amounts of data such as files or database entries.
Yet, there are some notable risk factors to keep in mind:
- Key distribution: The same key is used for both encryption and decryption, so it must be securely shared between parties. This creates a significant vulnerability during the key exchange, as interception or compromise of the key could lead to unauthorized access.
- Single point of failure: If the encryption key is compromised, all data encrypted with that key becomes accessible to unauthorized parties, and communications or stored data are no longer secure.
- Lack of scalability: In environments with many users or systems, managing unique keys for each pair of parties becomes increasingly complex and unmanageable. Private key encryption does not scale well for multi-user communication networks.
- Trust dependency: Both parties must trust each other to protect and use the key responsibly. A breach on either end could compromise the encrypted data.
Despite these limitations, private key encryption remains highly effective for use cases where the secure key exchange is feasible and scalability is not a concern, such as encrypting files, databases, or communications within a trusted network.
How does private key encryption work?
Private key encryption works by encoding plaintext using an encryption algorithm. In short, encryption algorithms are mathematical rules that determine how the key alters the encrypted data. There are typically two types:
- A block cipher that encrypts data into fixed-size blocks.
- A stream cipher that encrypts it one bit or byte at a time.
Depending on which cipher you choose, the private key process works like this:
- Key generation: The sender generates a secure, random encryption key with a cryptographic algorithm.
- Key exchange: They share the encryption key with the recipient, often through a protected channel or by combining it with an asymmetric encryption method.
- Data preparation: The sender formats the plaintext or divides it into specific blocks.
- Data encryption: The algorithm uses the encryption key to transform plaintext into ciphertext, rendering it unreadable without the key.
- Transmission: The sender transmits the ciphertext to the recipient or stores it securely for later use.
- Decryption: The recipient uses the same key to reverse the encryption process, converting the ciphertext back into plaintext.
Common private key encryption algorithms
Examples of symmetric or private key encryptions include the following algorithms:
- Data Encryption Standard (DES): Uses a 56-bit key and divides data into 64-bit blocks. Vulnerabilities led to its eventual deprecation.
- Triple Data Encryption Standard (3DES): Applies the same encryption algorithm three times to each block, increasing key size and security. NIST deprecated 3DES in 2019, citing known vulnerabilities.
- Advanced Encryption Standard (AES): Offers key lengths of up to 256 bits, rendering it more resistant to brute-force attacks.
In cryptography, quantum computing is a well-known and inevitable threat to modern encryption. Quantum offers exponentially more computing power than today’s most advanced technologies, allowing it to crack even the most sophisticated ciphers. Fortunately, symmetric encryption algorithms are considered less vulnerable to quantum attacks so long as the key length is sufficient.
Threats to private key encryption
Organizations that use private key processes must navigate several potential security risks, such as:
1. Key exposure
Key exposure occurs when a private encryption key is accidentally or maliciously revealed to unauthorized parties. This can happen due to improper storage, theft, or system vulnerabilities. Once exposed, attackers can use the key to decrypt sensitive data, impersonate the key owner, or sign malicious content, compromising the integrity and confidentiality of encrypted systems.
2. Brute-force attacks
Brute-force attacks involve bad actors systematically trying all possible key combinations until they find the correct one. While strong encryption algorithms with sufficiently large key sizes make these threats computationally infeasible, shorter or poorly chosen keys are vulnerable, especially with advancements in processing power or quantum computing.
3. Side-channel attacks
Side-channel attacks exploit information leaked during the encryption process, such as timing, power consumption, or electromagnetic emissions, to infer private keys. These attacks target the implementation of the cryptographic system rather than the algorithm itself, posing a serious threat to systems with insufficient hardware or software protections.
4. Poor key management
Ineffective key management activities include weak key generation, improper key storage, insufficient access controls, or failure to rotate keys regularly. These practices increase the risk of unauthorized access or misuse, potentially leading to data breaches or the inability to decrypt critical data when needed.
How to enhance private key encryption
Fortunately, there are several best practices organizations can employ to better secure their private keys:
- Use strong algorithms: Implement robust encryption standards like AES-256. Symmetric algorithms such as this are resistant to quantum attacks — a future but significant threat to modern cryptography.
- Implement key management solutions: Use tools like hardware security modules (HSMs) to secure keys with a strong root of trust. These solutions provide tamper-proof environments and automate key lifecycle management, reducing the risk of human error.
- Regularly rotate keys: Change encryption keys periodically to minimize exposure and limit the damage caused by compromised keys. Key rotation ensures that outdated keys are retired, reducing the risk of long-term vulnerabilities.
- Limit key access: Restrict access to private keys to essential personnel or systems, enforcing strict role-based controls. This minimizes the chance of accidental or malicious misuse and enhances accountability.
- Monitor and audit key usage: Track key usage to detect unauthorized activity. Regular audits provide insights into how keys are accessed and used, enabling faster response to potential threats.
- Educate employees: Train staff on best practices for handling encryption keys, including recognizing phishing attempts and securely storing keys. Informed employees act as a critical line of defense against human-error-induced breaches.
Protect your private keys with Entrust
Are you worried about securing your private keys? Entrust offers many solutions to help you protect your cryptographic assets and sensitive data.
With Entrust KeyControl, you gain centralized control over your keys in a decentralized, vault-based architecture. This ensures you’re not storing all your assets in one location. And, with nShield HSMs, you can perform cryptographic operations in a hardened environment.
Contact our team today to discover how Entrust can help you reap the benefits of private key encryption. Or, if you want to learn more, download our eBook below.