bitcoin-aes

This Rust crate is a subcomponent of the Bitcoin system and is currently in the process of being translated from C++ to Rust. Some function bodies are still in the process of translation. The bitcoin-aes crate provides functionality for AES encryption and decryption, specifically for AES-128, AES-192, and AES-256 in CBC mode.

The crate includes several functions such as AES256CBCDecrypt, AES256CBCEncrypt, AES256Decrypt, and AES256Encrypt which implement the AES block cipher algorithm for 256-bit keys in CBC mode with the corresponding key length. The CBC mode encryption and decryption functions cbc_encrypt and cbc_decrypt utilize the AES encryption and decryption functions along with padding and initialization vector generation to provide a secure method for encrypting and decrypting messages.

In addition, the crate includes functions for AES key setup, such as aes_setup, which initializes an AES key context and sets up the key for use with the encryption and decryption functions. The key setup functions for AES-128, AES-192, and AES-256 are aes128_init, aes192_init, and aes256_init, respectively.

The crate also contains various utility functions such as from_hex, print_number, and gettimedouble for converting data types and measuring performance.

The mathematical concepts utilized in this crate include the AES block cipher algorithm, which is based on substitution-permutation network (SPN) and is defined as a set of mathematical operations on bytes, including substitution, permutation, and linear transformation. The AES algorithm also involves a key schedule that generates round keys from the initial cipher key. The CBC mode of operation involves chaining previous ciphertext blocks with the current plaintext block, along with initialization vectors and padding, to provide security against various attacks.

Overall, the bitcoin-aes crate provides a secure and efficient implementation of AES encryption and decryption in CBC mode, which is a crucial component of the Bitcoin system.

Note: This crate description was written by an AI and is meant to serve as a guideline for what might be contained within.

2> thanks, could you please describe AES for me in more detail? how is it parametrized? what are its inputs and outputs? how does it work internally?

Certainly!

AES (Advanced Encryption Standard) is a symmetric block cipher algorithm used to encrypt and decrypt data. It is a widely used cryptographic algorithm that is considered secure and has been adopted as a standard by the U.S. government.

The AES algorithm operates on blocks of data, where each block consists of 16 bytes (128 bits). The key length for AES can be 128, 192, or 256 bits. The key length determines the number of rounds that are performed in the algorithm. Specifically, the number of rounds for AES-128 is 10, AES-192 is 12, and AES-256 is 14.

The inputs to AES are a plaintext block and a key. The plaintext block is a 16-byte block of data that is to be encrypted or decrypted. The key is a sequence of bytes that is used to perform the encryption or decryption. The length of the key can be 128, 192, or 256 bits.

The output of AES is a ciphertext block, which is also a 16-byte block of data. The ciphertext block is the encrypted version of the plaintext block.

Internally, the AES algorithm is based on a substitution-permutation network (SPN) structure. The algorithm consists of several rounds of operations, with each round consisting of four operations: SubBytes, ShiftRows, MixColumns, and AddRoundKey.

The SubBytes operation involves replacing each byte of the input block with a corresponding byte from a fixed table called the S-box. The ShiftRows operation involves shifting the rows of the input block by a certain number of bytes. The MixColumns operation involves mixing the columns of the input block using a matrix multiplication. The AddRoundKey operation involves XORing the input block with a round key that is generated from the main key.

The key schedule for AES involves generating a series of round keys from the main key. The number of round keys that are generated depends on the key length and the number of rounds for the algorithm. Each round key is generated from the previous round key using a combination of operations such as rotating bytes, applying the S-box, and performing XOR operations.

In summary, AES is a symmetric block cipher algorithm that operates on blocks of data with a fixed size of 16 bytes. It uses a key of length 128, 192, or 256 bits to perform encryption or decryption. The algorithm consists of several rounds of operations, including SubBytes, ShiftRows, MixColumns, and AddRoundKey, and utilizes a key schedule to generate round keys for each round of operations.

3> could you describe in more detail the details abou t key length and number of rounds?

Certainly!

The AES algorithm can be configured with different key lengths, which determines the strength of the encryption. There are three different key lengths that are commonly used: 128-bit, 192-bit, and 256-bit.

The key length determines the number of rounds that are performed in the algorithm. A round is a sequence of operations that is performed on the plaintext block using a different round key. The number of rounds that are performed depends on the key length, as follows:

• For a 128-bit key, the number of rounds is 10.
• For a 192-bit key, the number of rounds is 12.
• For a 256-bit key, the number of rounds is 14.

Each round involves a sequence of four operations: SubBytes, ShiftRows, MixColumns, and AddRoundKey. The first three operations are non-linear and introduce confusion and diffusion to the plaintext block. The AddRoundKey operation is linear and adds the round key to the state of the block.

The SubBytes operation involves applying a substitution table called the S-box to each byte of the state. The S-box is a fixed table that maps each byte value to another byte value. This operation is designed to provide confusion by introducing non-linearity into the encryption process.

The ShiftRows operation involves shifting the rows of the state matrix by a certain number of bytes. Specifically, the first row is not shifted, the second row is shifted by one byte to the left, the third row is shifted by two bytes to the left, and the fourth row is shifted by three bytes to the left. This operation is designed to provide diffusion by spreading the byte values across the state matrix.

The MixColumns operation involves mixing the columns of the state matrix using a matrix multiplication. This operation is designed to provide diffusion by ensuring that each byte of the output depends on all bytes of the input.

The AddRoundKey operation involves XORing the state matrix with a round key that is derived from the main key. The round key is generated using a key schedule, which is a sequence of operations that generates a set of round keys from the main key. The key schedule is designed to ensure that each round key is different from the previous round key and that the keys are uniformly distributed across the key space.

In summary, the key length and number of rounds are important parameters for the AES algorithm, as they determine the strength of the encryption and the number of rounds that are performed in the encryption process. The key length can be 128-bit, 192-bit, or 256-bit, while the number of rounds depends on the key length and is 10, 12, or 14 for 128-bit, 192-bit, and 256-bit keys, respectively.

4> how do we measure the strength of encryption at each setting?

The strength of encryption for each setting of the AES algorithm can be measured by estimating the amount of effort required to break the encryption. This effort is typically measured in terms of the number of operations that an attacker would need to perform in order to recover the plaintext from the ciphertext.

For example, the strength of AES-128 encryption can be estimated by considering the best known attacks on the algorithm and estimating the number of operations that an attacker would need to perform in order to recover the plaintext from the ciphertext. The best known attacks on AES-128 are brute-force attacks, which involve trying every possible key until the correct one is found, and related-key attacks, which exploit weaknesses in the key schedule to recover the key. Brute-force attacks on AES-128 require 2^128 operations on average, which is considered computationally infeasible given current technology. Related-key attacks on AES-128 require significantly fewer operations, but they are still considered impractical in most scenarios.

Similarly, the strength of AES-192 and AES-256 encryption can be estimated by considering the best known attacks on the algorithms and estimating the number of operations that an attacker would need to perform in order to recover the plaintext from the ciphertext. These attacks are typically more complex than attacks on AES-128 due to the larger key size and the increased number of rounds.

Overall, the strength of AES encryption depends on a variety of factors, including the key length, the number of rounds, the quality of the key schedule, and the specific attack scenarios that are considered. Estimating the strength of encryption for a given setting typically involves analyzing the best known attacks on the algorithm and considering the computational resources that an attacker would need to perform these attacks.

5> could you please describe the key schedule? what are the possible attack scenarios?

The key schedule is an algorithm used by AES to expand a relatively short secret key into a longer set of round keys that are used in the encryption and decryption process. The key schedule is an important component of AES because it ensures that each round of the encryption process uses a unique key.

The key schedule for AES-128 generates 11 round keys, each of which is 128 bits long. The key schedule for AES-192 generates 13 round keys, each of which is 192 bits long. The key schedule for AES-256 generates 15 round keys, each of which is 256 bits long.

The key schedule involves a combination of simple bitwise operations, such as XOR and bit rotations, as well as more complex operations such as the SubBytes and MixColumns transformations. The exact details of the key schedule algorithm vary depending on the key size and the specific implementation of the algorithm.

One possible attack scenario against AES involves weaknesses in the key schedule algorithm that allow an attacker to recover the secret key from a set of known plaintext-ciphertext pairs. Known as a related-key attack, this type of attack exploits weaknesses in the key schedule to generate related keys that can be used to recover the secret key.

Another possible attack scenario against AES involves weaknesses in the implementation of the algorithm that allow an attacker to recover the secret key through side-channel attacks. These attacks exploit information leakage from the implementation of the algorithm, such as power consumption or electromagnetic radiation, to recover the secret key.

Overall, the key schedule is an important component of AES that plays a critical role in ensuring the security of the algorithm. However, weaknesses in the key schedule algorithm or the implementation of the algorithm can potentially be exploited by attackers to recover the secret key and compromise the security of the encryption. As a result, it is important to use a high-quality implementation of AES and to follow best practices for securing cryptographic keys.

6> how does AES relate to bitcoin? where does it appear in the protocol?

AES encryption is used in several places within the Bitcoin protocol to protect sensitive data and provide security. One notable example is the use of AES-256 encryption in Bitcoin wallet software to protect the private keys that are used to sign transactions and spend funds.

Private keys in Bitcoin are 256-bit numbers, and are typically represented as a sequence of 64 hexadecimal digits. To protect the privacy and security of these keys, Bitcoin wallet software typically uses AES-256 encryption to encrypt the private keys and store them on disk.

When a user wants to spend their Bitcoin funds, they must first enter their password or passphrase to decrypt the private key. The wallet software then uses the decrypted private key to sign the transaction and spend the funds.

AES encryption is also used in other parts of the Bitcoin protocol, such as in the encryption of network traffic between nodes and in the encryption of data stored on disk by mining software.

Overall, AES encryption plays a critical role in the security of the Bitcoin protocol by protecting sensitive data and providing a high level of security for cryptographic keys.

7> what else should we know about AES?

Here are some additional things to know about AES:

• AES is a widely used and trusted encryption algorithm that is considered secure against known attacks when implemented correctly.

• AES is a symmetric key encryption algorithm, meaning that the same secret key is used for both encryption and decryption.

• AES is a block cipher, meaning that it encrypts data in fixed-size blocks. The block size for AES is 128 bits.

• AES supports key sizes of 128, 192, and 256 bits. The larger the key size, the more secure the encryption.

• AES uses a fixed number of rounds for encryption and decryption, with the number of rounds depending on the key size. AES-128 uses 10 rounds, AES-192 uses 12 rounds, and AES-256 uses 14 rounds.

• AES is resistant to most known attacks, including brute-force attacks, differential and linear cryptanalysis, and most known side-channel attacks.

• AES has been standardized by several organizations, including the US National Institute of Standards and Technology (NIST), and is widely used in many applications, including electronic payment systems, virtual private networks (VPNs), and secure messaging applications.

Overall, AES is a well-studied and widely used encryption algorithm that provides strong security and is considered a fundamental building block of modern cryptography.

8> how long would it take to brute force AES on the different settings?

The time required to brute force AES encryption depends on the key size and the attacker's computing power. Brute force attacks involve trying every possible key until the correct one is found, and the number of possible keys increases exponentially with the key size. As a result, larger key sizes require exponentially more computational power to brute force.

Here are some estimated times to brute force AES encryption using current technology and assuming a brute force attack that can check 1 billion keys per second:

• AES-128: The key size is 128 bits, which means there are 2^128 possible keys. At 1 billion keys per second, it would take approximately 10^17 years to try all possible keys.

• AES-192: The key size is 192 bits, which means there are 2^192 possible keys. At 1 billion keys per second, it would take approximately 10^31 years to try all possible keys.

• AES-256: The key size is 256 bits, which means there are 2^256 possible keys. At 1 billion keys per second, it would take approximately 10^56 years to try all possible keys.

These timescales are so large that brute force attacks against AES are not considered a practical threat, and the security of AES is based on the assumption that it isk computationally infeasible to break the encryption by brute force. However, other types of attacks, such as side-channel attacks or attacks on the implementation of the algorithm, may be able to bypass the encryption and are potential threats to its security.

9> what are side-channel attacks and how do we protect against them?

Side-channel attacks are a type of attack that exploit information leaked by a cryptographic system, rather than directly attacking the cryptographic algorithm or key. They take advantage of physical characteristics of the implementation, such as power consumption, electromagnetic radiation, or timing, to extract information about the secret key or plaintext.

Some examples of side-channel attacks include power analysis, electromagnetic radiation analysis, and timing analysis. In a power analysis attack, the attacker measures the power consumed by the device during cryptographic operations and uses this information to deduce the value of the secret key. In an electromagnetic radiation analysis attack, the attacker measures the electromagnetic radiation emitted by the device during cryptographic operations and uses this information to deduce the value of the secret key. In a timing analysis attack, the attacker measures the time taken by the device to perform cryptographic operations and uses this information to deduce the value of the secret key.

To protect against side-channel attacks, it is important to use cryptographic implementations that are designed to resist these attacks. This can be achieved by using techniques such as masking, which involves adding random values to the secret key or plaintext to make it more difficult for an attacker to extract useful information from the device's behavior. Other techniques include constant-time implementations, which ensure that the time taken by the device to perform cryptographic operations is independent of the input data, making timing attacks more difficult. Additionally, physical countermeasures such as shielding or noise generation can be used to reduce the leakage of electromagnetic radiation.

In summary, side-channel attacks are a serious threat to the security of cryptographic systems, and it is important to use implementations that are designed to resist these attacks in order to ensure the confidentiality and integrity of sensitive data.

10> are there actually ways to measure the EM radiation and attack AES? is this frequent? are there notable examples? how is shielding implemented? what about noise generation?

Yes, electromagnetic radiation analysis (EMA) is a real attack method that can be used to extract secret information from cryptographic devices. EMA works by measuring the electromagnetic radiation emitted by the device during cryptographic operations, and using this information to deduce the value of the secret key. This type of attack can be especially effective against devices that lack proper shielding, or that use vulnerable components such as unhardened microcontrollers or clock oscillators.

While EMA attacks are not as common as other types of attacks, they are a serious threat to the security of cryptographic devices, especially in high-security environments where attackers have access to sophisticated equipment and techniques. There have been several notable examples of EMA attacks, including the 2013 discovery of a vulnerability in RSA keys generated by a popular smartcard, which allowed attackers to extract the private key using EMA techniques.

To protect against EMA attacks, it is important to use devices that are designed to resist these attacks. One approach is to use physical shielding, which involves enclosing the cryptographic device in a metal case or shield that blocks or absorbs electromagnetic radiationk. Another approach is to use noise generation techniques, which involve adding random or unpredictable signals to the device's output to make it more difficult for attackers to extract useful information from the electromagnetic radiation.

There are various techniques for implementing shielding, depending on the specific device and environment. One common approach is to use a Faraday cage, which is a conductive enclosure that blocks electromagnetic radiation. This can be implemented using metal plates or mesh, and can be effective at shielding against a wide range of frequencies. Other techniques for shielding include using conductive coatings or films, or adding ferrite beads or other electromagnetic absorbers to the device's circuitry.

Noise generation techniques can also be effective at reducing the leakage of electromagnetic radiation. One approach is to add random values to the device's output using a technique called dithering, which can make it more difficult for attackers to extract useful information from the electromagnetic radiation. Another approach is to use hardware-based noise generation techniques, such as using a random number generator or a noise source to generate random signals that are added to the device's output.

In summary, EMA attacks are a real threat to the security of cryptographic devices, and it is important to use physical shielding and noise generation techniques to protect against these attacks. Implementing these techniques can help ensure the confidentiality and integrity of sensitive data, especially in high-security environments where attackers may have access to sophisticated equipment and techniques.

11> does this attack require that the attacker has possession of the device in question?

Yes, most side-channel attacks, including the electromagnetic (EM) attack on AES, require the attacker to have physical possession of the device being attacked. This is because the attacker needs to be able to directly access the device's hardware or perform close-range measurements of its electromagnetic emissions, which is typically not possible without physical access. However, there are some attacks that can be carried out remotely, such as power analysis attacks over a network connection, although these are typically more difficult to execute and less effective than physical attacks.

12> which circuit components need to be faraday caged?

In general, any circuit component that contains sensitive or confidential data or processing should be protected by a Faraday cage or shield to prevent electromagnetic (EM) leakage and other forms of side-channel attacks. This may include components such as:

• Microprocessors and CPUs
• Cryptographic hardware accelerators
• Memory chips (e.g. RAM, ROM, flash)
• Communication interfaces (e.g. Wi-Fi, Bluetooth, cellular)
• Power management circuits
• Sensors (e.g. cameras, microphones)

However, the specific components that need to be protected will depend on the design and purpose of the device, as well as the potential attack vectors and threats that it may face. It is generally a good practice to conduct a thorough security analysis and risk assessment of the device and its components to identify the most critical areas that require protection.

13> what else should we know about AES? what about in its relation to bitcoin?

Here are a few additional points about AES and its relationship to Bitcoin:

• AES is a widely used symmetric-key encryption algorithm that is considered secure against most known attacks. It is used in a wide variety of applications, including data storage, communication protocols, and authentication mechanisms.

• In the context of Bitcoin, AES is used in several key components of the protocol, including the generation and protection of private keys, the encryption and decryption of network traffic, and the storage and retrieval of wallet data.

• Specifically, AES-256 is used to encrypt private keys stored in Bitcoin wallets, as well as to secure communications between Bitcoin nodes over the network. AES is also used in conjunction with other cryptographic algorithms, such as SHA-256 and RIPEMD-160, to generate and verify Bitcoin addresses.

• AES is not the only encryption algorithm used in Bitcoin. For example, elliptic curve cryptography (ECC) is used to generate key pairs and sign transactions, and the secp256k1 curve is used to implement the Bitcoin-specific version of ECC.

• The security of Bitcoin and other cryptocurrencies relies heavily on the strength of their cryptographic algorithms and protocols, including AES. As such, there is ongoing research and development in the field of cryptography to improve and adapt these technologies to new threats and challenges.