Need

Secure encryption algorithm using strong elliptic curves

Context

• Usage of Swift for iOS and macOS app development
• Usage of Foundation for building responsive and mobile-first web applications
• Usage of CommonCrypto for cryptographic operations

Description

Non compliant code

        import Foundation
import CommonCrypto

let privateKey: SecKey = //...
let publicKey: SecKey = //...

let plainText = "Hello, World!"

let plainTextData = plainText.data(using: .utf8)!
let cipherTextData = SecKeyCreateEncryptedData(publicKey, .eciesEncryptionCofactorX963SHA256AESGCM, plainTextData as CFData, nil)! as Data

let decryptedData = SecKeyCreateDecryptedData(privateKey, .eciesEncryptionCofactorX963SHA256AESGCM, cipherTextData as CFData, nil)! as Data
let decryptedText = String(data: decryptedData, encoding: .utf8)
        
        

This Swift code snippet demonstrates encryption and decryption using the Elliptic Curve Integrated Encryption Scheme (ECIES). The encryption algorithm used is a combination of cofactor Diffie-Hellman key exchange (X963) and AES-GCM for symmetric encryption, with SHA-256 for hashing.

The plaintext "Hello, World!" is first converted to data. Then, the SecKeyCreateEncryptedData function is used to encrypt the plaintext data using the public key. The result is the ciphertext data.

The SecKeyCreateDecryptedData function is then used to decrypt the ciphertext data using the private key. The result is the decrypted data, which is converted back to a string.

The vulnerability lies in the use of a weak elliptic curve. The security of the encryption depends on the strength of the elliptic curve used. If a weak curve is used, the encrypted data can be decrypted by an attacker with sufficient computational resources.

Steps

• Replace the insecure elliptic curve algorithm with a secure one.
• Use a strong elliptic curve algorithm such as ECDSA or ECDH.
• Ensure that the chosen elliptic curve algorithm is recommended by security experts.
• Update the code to use the secure elliptic curve algorithm for encryption and decryption.
• Verify that the chosen algorithm provides sufficient security for the application's needs.
• Consider consulting with a cryptography expert to ensure the correct implementation of the secure elliptic curve algorithm.

Compliant code

        import Foundation
import CommonCrypto

let privateKey: SecKey = //...
let publicKey: SecKey = //...

let plainText = "Hello, World!"

let plainTextData = plainText.data(using: .utf8)!
let cipherTextData = SecKeyCreateEncryptedData(publicKey, .eciesEncryptionStandardVariableIVX963SHA256AESGCM, plainTextData as CFData, nil)! as Data

let decryptedData = SecKeyCreateDecryptedData(privateKey, .eciesEncryptionStandardVariableIVX963SHA256AESGCM, cipherTextData as CFData, nil)! as Data
let decryptedText = String(data: decryptedData, encoding: .utf8)
        
        

The updated code now uses a secure elliptic curve algorithm for encryption and decryption. The insecure .eciesEncryptionCofactorX963SHA256AESGCM algorithm has been replaced with the secure .eciesEncryptionStandardVariableIVX963SHA256AESGCM algorithm.

This secure algorithm is recommended by security experts and provides sufficient security for the application's needs. It uses a variable initialization vector (IV) and combines the X9.63 key derivation function with the SHA-256 hash function and the AES-GCM encryption algorithm.

The SecKeyCreateEncryptedData function is used to encrypt the plain text data using the public key and the secure elliptic curve algorithm. The SecKeyCreateDecryptedData function is used to decrypt the cipher text data using the private key and the same secure elliptic curve algorithm.

The decrypted text is then converted back into a string using the UTF-8 encoding.

It is recommended to consult with a cryptography expert to ensure the correct implementation of the secure elliptic curve algorithm.

References

• 421. Insecure encryption algorithm - Insecure Elliptic Curve