AES encryption: how does it safeguard your data?

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Today, the primary method of information storage is digital, which is something hackers are well aware of. Consequently, threats targeting data security have increased relatively quickly, with businesses becoming the primary targets. This sets forth a precedent to balance data availability, ease of use, and security, enabling them to carry out daily operations while ensuring the confidentiality of sensitive data.

Businesses must ensure that they can perform their daily operations smoothly while guaranteeing data confidentiality. Advanced Encryption Standard (AES) was developed to address this challenge — an encryption algorithm that has become the de facto standard for protecting electronic data. In this article, we'll explore what the AES encryption algorithm is, how it works, its features, and its security capabilities. We'll also compare the Advanced Encryption Standard to other encryption methods.

What is AES?

AES stands for Advanced Encryption Standard, a specification for the encryption of electronic data. It was established by the United States National Institute of Standards and Technology (NIST) in 2001. Since then, it has become a widely used algorithm for symmetric key encryption.

The advanced encryption algorithm is based on the Rijndael cipher developed by two Belgian cryptographers, Joan Daemen and Vincent Rijmen, who submitted it to the NIST during the Advanced Encryption Standard selection process. As a block cipher, AES encrypts data in fixed-size blocks, so 128, 192, or 256 bits in length. This makes up various AES designations like AES-128, AES-192, and AES-256.

Advanced Encryption Standard has been extensively tested and is considered secure against all known practical attacks (like brute forcing) when used properly. For this reason, it's used worldwide in various applications, including secure communications, file transfers, and storage.

AES implementation types

AES can be implemented using different modes of operation. They introduce new ways to apply symmetric block cipher to encrypt or decrypt data. The choice of implementation depends on the specific requirements of the application and the desired security properties. Here are its most commonly used types:

ECB (Electronic Codebook). Divides plaintext into blocks; each block is encrypted independently using the AES algorithm. This mode is simple and parallelizable, but it is unsuitable for encrypting large amounts of data or when there is repetitive data, as it can lead to patterns in the ciphertext.

CBC (Cipher Block Chaining). XORs each plaintext block with the previous ciphertext block before encryption. This introduces a dependency between blocks, making it more secure than ECB against pattern analysis attacks. Initialization Vector (IV) is used to encrypt the first block, and the ciphertext of each block is used as the IV for the next block.

CTR (Counter). Converts the block cipher AES into a stream cipher. It uses a counter value combined with a unique nonce (number used once) as the input to the AES algorithm. The resulting output is XORed with the plaintext to produce the ciphertext. CTR mode allows parallel encryption and decryption and is commonly used in scenarios where random access to encrypted data is required.

OFB (Output Feedback). Also converts AES into a stream cipher. It generates a keystream by encrypting an IV with AES and then XORs the keystream with the plaintext to produce the ciphertext. Unlike CTR, OFB requires sequential encryption and decryption, as errors in transmission can propagate to subsequent blocks.

CFB (Cipher Feedback). Very similar to OFB but operates on smaller units, typically individual bytes. It encrypts the IV and XORs the resulting output with the plaintext to produce the ciphertext. The keystream is then generated by encrypting the previous ciphertext block. Like OFB, CFB requires sequential processing.

GCM (Galois/Counter Mode). Combines AES encryption with a cryptographic hash function called GHASH. It provides both confidentiality and integrity of the data. GCM mode is commonly used in network communication protocols and is suitable for parallel processing.

Remember that these are just a few examples of AES encryption modes. The best choice for a specific use case will depend on factors like security requirements, performance, parallelizability, and specific needs of the application.

How AES encryption works

Fixed-length blocks of data (so 128, 192, or 256 bits) are transformed as a series of substitutions, permutations, and mixing operations are applied to encrypt and decrypt the data. As AES encryption uses a symmetric key, the same one is used for encryption and decryption.

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The process occurs in stages:

1. Key expansion. The initial key is expanded into 44, 52, or 60 32-bit words for 128, 192, and 256-bit keys. These expanded words are used in the subsequent rounds of AES encryption. The key expansion process involves generating additional round keys from the initial key.

2. Initial round. The input or plaintext block is mixed with the initial round key before proceeding to the main rounds of AES encryption.

3. Each round of AES encryption consists of four transformations:

  • SubBytes. Each byte in the block is replaced with its corresponding byte in a predefined substitution box designed to resist known cryptographic attacks.

  • ShiftRows. Bytes in each block row are shifted cyclically to the left, with different offsets for different rows. This step ensures that each column of the output state of the ShiftRows operation is composed of bytes originating from each column of the input state.

  • MixColumns. Each column is transformed using a matrix multiplication operation, which provides diffusion and enhances the security of AES. This operation affects all four bytes in a column together.

  • AddRoundKey. The resulting block is combined with the round key derived from the key schedule. This step combines the data with the key, providing diffusion.

4. Finalization. After all the main rounds, a final round is performed, including all the steps except MixColumns.

5. Output. The resulting bits are the ciphertext corresponding to the input plaintext block.

Decryption is performed with the reverse operations in the opposite order. The key schedule is used directly (not reversed) to derive the round keys for decryption.

What are the features of AES?

AES is one of the most popular algorithms for securing sensitive data. Here are some key features that make it a robust encryption algorithm.

  • Symmetric key encryption. AES uses the same key for encrypting and decrypting data. This is different from other setups, using different keys for each stage. 

  • Key sizes. AES supports various key sizes like 128, 192, and 256 bits. These different versions mean that the larger the key is, the stronger the encryption is. On the other hand, this also means that more computational resources are needed.

  • Security and efficiency. AES is one of the algorithms without any practical cryptanalytics attacks performed. In addition, it's also relatively fast and efficient in both hardware and software implementations.

  • Widely accepted standard. AES is a de facto standard when securing wireless networks, VPNs, SSL/TLS for secure web browsing, and more.

  • Open-source. AES is an open standard. It's freely available to the public and can be implemented in any software or hardware without paying royalties.

Is AES secure?

AES encryption is considered highly secure. Its widespread adoption and extensive analysis by security experts have field tested its resilience against cryptographic attacks. Currently, AES is believed to be resistant to all known practical attacks. That said, its security depends not only on the strength of the encryption algorithm itself but also on its use. Using a predictable or easily guessable encryption key could render AES ineffective.

While AES encryption is secure against cryptographic attacks, it's also important to note that it's not immune to other hacking attempts. Methods like side-channel attacks, which involve gaining information from the physical implementation of the cryptosystem rather than weaknesses in the algorithm itself, or social engineering attacks can still pose threats.

Future developments of technology in the fields like quantum computing could potentially impact the security of AES. Large-scale quantum computers, if they become widely accessible, could theoretically break AES, but this remains a distant prospect.

What's the difference between AES-128 and AES-256?

AES-128 vs AES-256 comparison

The main difference between AES-128 and AES-256 lies in their key length. They both refer to different versions of the AES standard, with the numbers referring to the length of the encryption key used in bits:

  • AES-128 uses a 128-bit key length. It's quicker and requires less computational power. The key space is huge and generally considered very secure and suitable for most purposes.

  • AES-256 uses a 256-bit key length. It's slightly slower and requires more computational power due to the longer key. However, it provides a significantly larger key space, making it even harder for an attacker to guess the key. This makes it more secure than AES-128.

In practical terms, the security difference between AES-128 and AES-256 is relatively minimal. Both are considered secure and suitable for encrypting sensitive information.

What's the difference between AES vs. DES?

DES encryption vs. AES encryption comparison table

AES and DES (Data Encryption Standard) are both symmetric key encryption methods, but they differ in various aspects like security, key size, block size, and round of operation.

AES allows key sizes of 128, 192, and 256 bits, making it more flexible and secure. Regardless of key size, it uses a block size of 128 bits. Also, the number of rounds in AES varies based on the key size (10 for 128-bit, 12 for 192-bit, and 14 for 256-bit). Due to its large key sizes, this algorithm is very secure and efficient. As it's based on a design principle known as a substitution-permutation network (a combination of both substitution and permutation) and is fast in software and hardware.

Meanwhile, DES uses a fixed key size of 56 bits with a block size of 64 bits, which is relatively small and susceptible to brute-force attacks. As the key size is always fixed, DES always operates in 16 rounds. With enough computational power, DES is less secure and can be broken. Its cousin, 3DES, applies the DES algorithm three times to each data block, but it's slower and less efficient than AES. DES is based on the so-called Feistel network, a symmetric structure used in most block cipher algorithms, which is still not as efficient as AES.

In conclusion, AES is a more robust and efficient encryption standard than DES in the modern computing landscape. For this reason, DES has been rendered largely obsolete due to its susceptibility to brute-force attacks and overall lower performance.

What's the difference between AES vs. RSA?

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While AES is a symmetric block cipher, RSA (Rivest-Shamir-Adleman) is an asymmetric encryption algorithm. AES is primarily used for encrypting data in transit and at rest. RSA is mainly used for secure data transmission, key exchange protocols, digital signatures, and small data encryption.

  • AES — uses symmetric keys to encrypt and decrypt data, so it's faster, but the encryption key must be shared securely. The used key sizes are 128, 192, and 256 bits. Overall, AES is much faster and more efficient, particularly for encrypting large data.

  • RSA — uses asymmetric keys: a public key shared with everyone and a private key that's kept secret and is used for encryption. RSA key sizes must be much larger to match equivalent security to AES, so 1024 to 4096 bits long. Due to its complexity and size RSA is rarely used for encrypting large amounts of data.

However, in practice, many systems use a combination of both RSA and AES. For example, RSA is used to securely share an AES key, which is then used to encrypt the actual data. This approach combines the speed and efficiency of AES with the convenience and security of RSA's public-key system.

How does NordLayer incorporate AES encryption?

NordLayer encrypts data in transit using AES-256 or ChaCha20 ciphers (depending on the selected tunneling protocol. When OpenVPN and IKEv2 tunneling protocols are enabled, they use AES-256 encryption, while NordLynx uses ChaCha20. This leverages advanced encryption capabilities to ensure robust electronic data protection.

By utilizing AES encryption algorithms with a key length of up to 256 bits, NordLayer secures sensitive data transmitted across networks, protecting it from unauthorized access and interception. NordLayer's implementation of AES encryption ensures the confidentiality and integrity of data, offering users peace of mind that their business communication is safe.

Contact NordLayer today to discuss your options for creating secure data exchange and access.

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