Certified: The Security+ Prepcast

In this episode, we are examining cryptographic attack indicators—specifically, how to identify and respond to downgrade attacks and hash-based collision exploits, including birthday attacks. While cryptographic systems are designed to protect data, flaws in their implementation or negotiation can be used against them. These types of attacks don’t break encryption directly—they undermine its strength or predictability. Recognizing the signs of these attacks helps organizations respond quickly and improve the resilience of their cryptographic infrastructure.
Let’s start with downgrade attacks. A downgrade attack occurs when an attacker manipulates a cryptographic negotiation to force the use of a weaker or outdated algorithm. This typically happens during the handshake phase of a secure connection—like when a browser connects to a website using HTTPS. If the attacker is able to intercept and influence the negotiation, they may trick the client and server into agreeing on an older, less secure protocol or cipher.
The goal is to reduce the strength of the encryption being used so it becomes easier to break. Once the connection is downgraded, the attacker may attempt to intercept, decrypt, or modify the data in transit.
Indicators of a downgrade attack include unexpected use of older versions of Transport Layer Security, such as TLS version one or version one point one, when version one point two or one point three is normally supported. You may also see sessions using weak cipher suites, like those with key lengths shorter than one twenty-eight bits or using broken algorithms like RC Four.
Logs and traffic analysis tools may reveal anomalies in the handshake process, especially if the downgrade is repeated across multiple sessions. Certificate errors, unusually slow connections, or protocol mismatches can also point to attempted interference.
To prevent downgrade attacks, organizations should configure systems to use only modern, secure cryptographic protocols. This includes disabling SSL and early TLS versions, rejecting weak cipher suites, and enforcing the use of Transport Layer Security version one point two or higher. Certificate pinning, secure renegotiation settings, and strong certificate validation can further reduce risk. Security tools should be configured to alert on handshake downgrades or the use of deprecated algorithms.
Now let’s turn to collision and birthday attacks. These threats target the reliability of hashing functions—the cryptographic tools used to generate a fixed-length output, or hash, from variable input data. Hashes are used to verify file integrity, sign digital messages, and authenticate data without revealing the original content.
A collision occurs when two different inputs produce the same hash value. If an attacker can create a second input with the same hash as a trusted file, they can potentially substitute malicious data without detection. This undermines the trust placed in digital signatures and hash-based verification systems.
The birthday attack is a specific type of collision attack that relies on probability theory. It’s based on the birthday paradox—the idea that in a room of just twenty-three people, there’s a high chance two people share the same birthday. In cryptography, this means that an attacker can find two inputs with the same hash faster than expected using brute force.
Indicators of collision attacks are harder to detect directly. Instead, they often surface during integrity checks that fail unexpectedly, or when trusted files are modified but still pass validation due to compromised hashes. For example, if a digital certificate is forged using a hash collision, systems may treat it as valid despite the underlying data being manipulated.
The best defense against these attacks is to use modern, collision-resistant hash functions. Algorithms like Secure Hash Algorithm two fifty-six or Secure Hash Algorithm three are currently considered secure. Older algorithms like MD Five and SHA One should be completely disabled, as they are known to be vulnerable.
Cryptographic systems should also use salted hashes and time-stamped digital signatures to make collisions harder to exploit. Using HMAC—Hashed Message Authentication Code—instead of plain hashes for authentication adds another layer of protection, since the secret key used in the hash is unknown to the attacker.
In high-security environments, hash values should be verified not just for consistency, but also for authenticity—meaning that the source of the hash should be known and trusted. This is where digital certificates, chain-of-trust verification, and secure key storage become essential.
As you prepare for the Security Plus exam, understand that cryptographic attacks don’t always come from brute force—they can exploit weaknesses in protocol negotiation and hash reliability. You may be asked to identify symptoms of a downgrade attack, such as the use of weak cipher suites, or to recommend how to defend against hash collisions. Focus on best practices for cryptographic configuration, modern algorithm use, and secure authentication processes.