CWE-1255: Comparison Logic is Vulnerable to Power Side-Channel Attacks
A device's real time power consumption may be monitored during security token evaluation and the information gleaned may be used to determine the value of the reference token.
View on MITREExtended Description
The power consumed by a device may be instrumented and monitored in real time. If the algorithm for evaluating security tokens is not sufficiently robust, the power consumption may vary by token entry comparison against the reference value. Further, if retries are unlimited, the power difference between a "good" entry and a "bad" entry may be observed and used to determine whether each entry itself is correct thereby allowing unauthorized parties to calculate the reference value.
Technical Details
- Structure
- Simple
Applicable To
Security Consequences
Scope
Impact
As compromising a security token may result in complete system control, the impacts are relatively universal.
Mitigation Strategies
Phase
Description
The design phase must consider each check of a security token against a standard and the amount of power consumed during the check of a good token versus a bad token. The alternative is an all at once check where a retry counter is incremented PRIOR to the check.
Phase
Description
Another potential mitigation is to parallelize shifting of secret data (see example 2 below). Note that the wider the bus the more effective the result.
Phase
Description
An additional potential mitigation is to add random data to each crypto operation then subtract it out afterwards. This is highly effective but costly in performance, area, and power consumption. It also requires a random number generator.
Phase
Description
If the architecture is unable to prevent the attack, using filtering components may reduce the ability to implement an attack, however, consideration must be given to the physical removal of the filter elements.
Phase
Description
During integration, avoid use of a single secret for an extended period (e.g. frequent key updates). This limits the amount of data compromised but at the cost of complexity of use.
Detection Methods
No detection method information available for this CWE.
Code Examples & CVEs
Demonstrative Examples
Consider an example hardware module that checks a user-provided password (or PIN) to grant access to a user. The user-provided password is compared against a stored value byte-by-byte.
Since the algorithm uses a different number of 1's and 0's for password validation, a different amount of power is consumed for the good byte versus the bad byte comparison. Using this information, an attacker may be able to guess the correct password for that byte-by-byte iteration with several repeated attempts by stopping the password evaluation before it completes.
Consider an example hardware module that checks a user-provided password (or PIN) to grant access to a user. The user-provided password is compared against a stored value byte-by-byte.
Since the algorithm uses a different number of 1's and 0's for password validation, a different amount of power is consumed for the good byte versus the bad byte comparison. Using this information, an attacker may be able to guess the correct password for that byte-by-byte iteration with several repeated attempts by stopping the password evaluation before it completes.
This code demonstrates the transfer of a secret key using Serial-In/Serial-Out shift. It's easy to extract the secret using simple power analysis as each shift gives data on a single bit of the key.
This code demonstrates the transfer of a secret key using a Parallel-In/Parallel-Out shift. In a parallel shift, data confounded by multiple bits of the key, not just one.
This code demonstrates the transfer of a secret key using Serial-In/Serial-Out shift. It's easy to extract the secret using simple power analysis as each shift gives data on a single bit of the key.
This code demonstrates the transfer of a secret key using a Parallel-In/Parallel-Out shift. In a parallel shift, data confounded by multiple bits of the key, not just one.
Observed CVE Examples (1)
CWE Relationships
No relationship information available for this CWE.
Frequently Asked Questions
What is CWE-1255: Comparison Logic is Vulnerable to Power Side-Channel Attacks?+
CWE-1255: Comparison Logic is Vulnerable to Power Side-Channel Attacks is a Common Weakness Enumeration (CWE) entry maintained by MITRE. A device's real time power consumption may be monitored during security token evaluation and the information gleaned may be used to determine the value of the reference token. The power consumed by a device may be instrumented and monitored in real time. If the algorithm for evaluating security tokens is not sufficiently robust, the power consumption may vary by token entry comparison against the reference value. Further, if retries are unlimited, the power difference between a "good" entry and a "bad" entry may be observed and used to determine whether each entry itself is correct thereby allowing unauthorized parties to calculate the reference value.
What are the security consequences of Comparison Logic is Vulnerable to Power Side-Channel Attacks?+
If exploited, CWE-1255 (Comparison Logic is Vulnerable to Power Side-Channel Attacks) it can compromise Confidentiality, Integrity, Availability, Access Control, Accountability and Authentication, leading to outcomes such as Modify Memory, Read Memory, Read Files or Directories, Modify Files or Directories, Execute Unauthorized Code or Commands and Gain Privileges or Assume Identity.
How do you prevent or mitigate Comparison Logic is Vulnerable to Power Side-Channel Attacks?+
Recommended mitigations for CWE-1255 include: The design phase must consider each check of a security token against a standard and the amount of power consumed during the check of a good token versus a bad token. The alternative is an all at once check where a retry counter is incremented PRIOR to the check. Another potential mitigation is to parallelize shifting of secret data (see example 2 below). Note that the wider the bus the more effective the result. An additional potential mitigation is to add random data to each crypto operation then subtract it out afterwards. This is highly effective but costly in performance, area, and power consumption. It also requires a random number generator.
Which programming languages are affected by Comparison Logic is Vulnerable to Power Side-Channel Attacks?+
CWE-1255 commonly affects Not Language-Specific. Note that weaknesses are often language-agnostic patterns, so secure coding practices apply broadly.
What are real-world examples of Comparison Logic is Vulnerable to Power Side-Channel Attacks?+
MITRE documents real CVEs mapped to CWE-1255, including CVE-2020-12788. You can look up the full details of each CVE, including CVSS scores and remediation guidance, on our CVE Lookup tool.
What is the difference between a CWE and a CVE?+
A CWE (Common Weakness Enumeration) like CWE-1255 describes a category of software weakness — the underlying flaw type. A CVE (Common Vulnerabilities and Exposures) identifies a specific, real-world vulnerability in a particular product. In short, a CWE is the kind of mistake, and a CVE is an instance of that mistake being found in software.