What is Symmetric Encryption

If encryption is not implemented properly, it poses security risks. To illustrate, let’s take a recent real-world example from the Group Health Cooperative of South Central Wisconsin (GHC-SCW). In January 2024, the hackers gained unauthorized access to the organization’s network and tried to encrypt the patient’s data. Although this effort failed, the malicious attackers still managed to access the database containing the patients’ sensitive information, including their credentials, social security numbers, insurance details, etc. That compromised data belonging to over 5,30,000 individuals.

If strong symmetric encryption had been implemented, the sensitive data compromise could have been prevented. This is because even if the attackers had infiltrated the security perimeter, the data would have been in an unreadable form. This attack clearly demonstrates the extent to which all organizations are at risk when strong encryption is not employed on their data.

Introduction

Symmetric encryption uses a single key for both encryption and decryption, with this key shared among all parties involved. This shared cryptographic key approach ensures fast and secure data transfers, as each party can encrypt and decrypt information using the same key, but it requires a secure method for key exchange.

Working

A private key shared exclusively between the sender and receiver is used to encrypt and decrypt data by employing an encryption algorithm. The data is first scrambled into ciphertext using this algorithm that makes the data not readable in any form while in transit. When the data reaches its destination, the recipient receives the ciphertext and, with the same key, decodes the data. The protection that this method offers depends solely on the secret and effective use of the key, whose access by an outside third party would be a threat to the entire system.  

The Process of Key Generation

In symmetric encryption, private keys are always created with the help of special techniques that ensure the keys are generated in a manner that is both random and strong. Simple random number functions are not enough; in this case, attacker-proof Cryptographically Secure Pseudorandom Number Generators (CSPRNGs) such as the Blum Blum Shub are used to eliminate all attacks based on patterns. To further enhance security, more sophisticated methods are applied, including the application of elliptic curves in key pair generation together with secure hash algorithms, ensuring each key is unique and challenging to guess. This strong key generation method is crucial in the encryption of data because if the keys produced are weak or predictable, they can be compromised, threatening data confidentiality and posing a risk to data integrity.

Symmetric encryption has two methods for encrypting data. Those two types are as follows

1. Block Encryption: According to this algorithm, cipher text blocks are generated from a constant amount of data bits.
2. Stream Encryption: In stream cipher, data is converted one bit at a time to the cipher text.

Can Symmetric Encryption systems be hacked?

Despite being a reliable method for securing sensitive information, symmetric encryption still faces certain threats. To break an adversary’s symmetric encryption system, there are two aspects that they must find out, the first being the secret key and the second being the encryption algorithm. These two aspects are the beliefs on which the encryption’s strength is based, so any breach in their security may result in sensitive information being made available to an undesirable party.

Advanced cryptanalysis is the primary method used by adversaries seeking to break symmetric encryption, which involves mathematical methods being applied to discover weaknesses in the encryption methods. Central to this approach is the “ciphertext-only attack” which refers to an approach where an attacker has access to the encrypted contents of a message only, and applies analysis over the ciphertext, that enables the deciphering of the secret key without ever directly accessing it.

NIST Recommendations for Securing Symmetric Encryption Keys

Several factors influence the strength of the symmetric encryption keys. They are as follows

• Length of the key bit size

  It is recommended to use longer keys so as to resist brute-force attacks. For instance, in the case of AES encryption, NIST specifies the use of a 256-bit key size for provision against future computing technologies like quantum computers.

  When it comes to key length, the encryption algorithm used, and the security required determine the length of the key selected. NIST also gives recommendations on the appropriate key size for various algorithms such as AES and others.

• Randomness

  The NIST emphasizes the importance of high-quality randomness, which is unpredictable in the process of key generation. Such randomness, ideally, is taken from a safe origin, such as a cryptographically secure pseudorandom number generator (CSPRNG).

  For example, SP 800-90A provides ‘Recommendation for Random Number Generation’ so that no pattern and regularity are predictable.

• Key generation

  It is vital that the key generation system make certain that the keys produced are both unpredictable and unique to each instance. In NIST’s recommendations, it is clearly pointed out that any key-generating process should avoid applying any method that is weak or can be easily predicted, such as system timestamps.

• Key Management, Rotation, and Destruction

  As part of its key management guidelines, NIST emphasizes the need to follow secure practices when it comes to storage, distribution, and use of keys. Furthermore, there should be regular rotation of keys in order to lower risks raised by long-time use of the same keys. Old keys should also be revoked to avoid unwanted access, and old keys should be destroyed to prevent unauthorized recovery. All of these processes, as well as the policies concerning secure access, rotation, and destruction of keys, should be implemented through key management systems.

• Access Control

  Access to symmetric keys should be limited according to the principle of Role Based Access Control and Identity Access Mangement. Only personnel or systems that are authorized to use the keys should be granted access.

  There need to be provisions for monitoring key usages and activities such as logging and audit so as to prevent or mitigate who tries to misuse keys or access them without authorization for ensuring causal security.

Advantages of Symmetric Encryption

1. Speed and Efficiency

   Symmetric techniques employ a single key for both encryption and decryption, which makes the advancement of such technologies less complex.

   This is largely due to the fact that this particular approach uses efficient methods of performing computational processes that do not take up much operational time. In this sense, the efficiency of symmetric encryption becomes even more important for applications with low latency and high throughput, such as the protection of real-time voice communications, bulk data transfers, or network-level security protocols such as IPsec and SSL/TLS.

2. Low Computational Overhead

   The design of symmetric key algorithms is based on factors that minimize the cost of computation; hence, they are appropriate in situations where encryption and decryption processes must happen in real-time.

   In contrast, the key techniques that are used in asymmetric encryption are the modular arithmetic-based key techniques, which are very resource-intensive. On the other hand, symmetric encryption algorithms rely on simple bit manipulations with less requirement on the system. Therefore, this makes symmetric encryption suitable for low-powered systems or applications that do not have high processing requirements, such as embedded systems, including mobile applications and IoT devices.

3. High Security

   Symmetric encryption algorithms, which include AES-256, offer great security through larger key sizes and system designs that are resistant to modern cryptographic attacks, especially brute-force or different cryptanalysis attacks.

   One such design is AES-256, which works with a 256-bit key and is well recognized for its massive security in theoretical as well as practical scenarios of cryptography. Together with efficient controls for protecting the encryption keys, such as hardware security modules (HSM) for key storage and short-time duration session keys, symmetric encryption expands its ability to safeguard the confidentiality of data in several areas, from the transmission of sensitive information to disk encryption.

4. Scalability for Large Data Sets

   Because of its faster execution speed, symmetric encryption is naturally suitable for processing and transmitting large quantities of data. In contrast, asymmetric encryption is not efficient for encrypting bulk data because it requires a lot of time and computational power to encrypt and then later decrypt messages.

   Symmetric encryption’s less operational time makes it useful in instances involving large data sets or data streaming, such as securing video streaming, etc.

5. Widely Adopted and Versatile

   Symmetric encryption is one of the pillars and is extensively used in protocols for TLS/SSL, VPNs (OpenVPN), disk encryption (BitLocker), and many more. This is due to its efficiency and compatibility with the technology. Since symmetric encryption is almost always used together with other encryption techniques (for example, public-key cryptography for encrypting the symmetric keys), it allows for high performance. Therefore, it is widely adopted.

Disadvantages of Symmetric Encryption

1. Key Distribution Problem

   The cryptographic shared key in symmetric encryption has to be distributed over discrete channels with high risks of information leakage. If the insecure channel gets intercepted and someone gets hold of the key, then the security of the communication is compromised. Thus, additional protocols, e.g., Diffie-Hellman or any other supported public-key infrastructures, must be used to prevent exposure while distributing the keys.

2. Scalability Issues

   In symmetric encryption, each unique pair of users is required to have a unique key, which causes the key management to grow exponentially with the total number of users. This increases the problem of scalability to a great extent, especially in environments where users are dynamic and keep changing, as that creates a lot of administration burden and threats to security.

3. Lack of Non-Repudiation

   As the same key is used for both encryption and decryption, there is no non-repudiation guarantee in symmetric encryption. Since there is no proof of source, this makes it impossible to use such functions in applications where accountability is required, such as digital signatures or money exchanges.

4. Key Management Complexity

   Symmetric key management, which includes the processes of generation, distribution, storage, rotating management, and revocation management of keys, becomes a tedious task when the number of keys on increases. Vulnerabilities are introduced due to poor key management, which requires safe management system solutions like hardware security modules (HSMs) essential for secure handling.

5. Vulnerability to Key Compromise

   If the secret key is disclosed, all data that was protected with this key will no longer stay protected. This is because, in symmetric encryption, a single key is used for both operations, where, if the key is revealed, it is possible to read every other encrypted text protected by that key. Hence, changing the keys often and keeping them away from the public is very important.

Use Cases

Data-at-Rest Encryption

Data at rest in information technology concerns with digital information that is maintained or exists in a fixed location on various storage facilities, such as cloud storage, file storage services, relational databases, non-relational databases, and data warehouses. The information can be divided into two main groups, which are structured data, for example data contained in tables or schemas or uses spreadsheets and unstructured data such as text, video, images, and log files.

Different services utilize symmetric encryption to protect data backups. For instance, both AWS and IBM Cloud suggest using AES-256 for server-side encryption (SSE) in transit and, at rest, protecting the data with the highest level of confidentiality and industry standards. This high-strength encryption is critical in preventing any unauthorized access to protected information in the cloud.

Virtual Private Networks (VPNs)

Symmetric security is applied in a VPN to produce an encrypted tunnel over which the information may be transmitted securely between the client and its hosts. In symmetric encryption, we use a shared key for both encryption and decryption to make it possible for only the sender and its associated receiver to read what is being sent. Typically, VPNs use encryption protocols like AES (Advanced Encryption Standard) in combination with secure key exchange methods (like Diffie-Hellman or ECDH) to securely share the symmetric key over the network.

The various VPNs use several strong algorithms to offer high-level security; for instance, the VPN protocols OpenVPN, which is free software, and SSTP, which was created by Microsoft, are both reliant on AES-256 in ensuring that data transmission is secure, especially where there is a high-security concern such as in preventing man-in-the-middle attacks.

Wireless Network Security (Wi-Fi)

Common protocols used in Wireless Fidelity networks are WPA (Wi-Fi Protected Access), WPA2, and the newest one, WPA3. These protocols are used to allow wireless communication securely.

To ensure the security, these protocols apply symmetric encryption to protect data in motion and ensure confidentiality and integrity without compromising the performance of wireless communication.

Conclusion

Symmetric encryption stands out as one of the most acceptable ways to keep your information safe. Symmetric key cryptography allows ciphering and deciphering by the use of a common secret key, from which the allowable entities can only obtain the requisite secure data.

Organizations need to prepare for rising cybersecurity threats by enforcing strong symmetric encryption algorithms like AES, Blowfish, and Twofish to prevent unauthorized access or data leaks of any kind.