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Weakness · High

CWE-327: Use of a Broken or Risky Cryptographic Algorithm

What it is

The product uses a broken or risky cryptographic algorithm or protocol.

Likelihood of exploit: HighMITRE CWE 4.19.1

Severity (our rating)
High
Likelihood of exploit
High
Introduced during
Architecture and Design, Implementation
Exploited in the wild
No CVE in CISA's catalog

In more detail

Cryptographic algorithms are the methods by which data is scrambled to prevent observation or influence by unauthorized actors. Insecure cryptography can be exploited to expose sensitive information, modify data in unexpected ways, spoof identities of other users or devices, or other impacts. It is very difficult to produce a secure algorithm, and even high-profile algorithms by accomplished cryptographic experts have been broken. Well-known techniques exist to break or weaken various kinds of cryptography. Accordingly, there are a small number of well-understood and heavily studied algorithms that should be used by most products. Using a non-standard or known-insecure algorithm is dangerous because a determined adversary may be able to break the algorithm and compromise whatever data has been protected. Since the state of cryptography advances so rapidly, it is common for an algorithm to be considered "unsafe" even if it was once thought to be strong. This can happen when new attacks are discovered, or if computing power increases so much that the cryptographic algorithm no longer provides the amount of protection that was originally thought. For a number of reasons, this weakness is even more challenging to manage with hardware deployment of cryptographic algorithms as opposed to software implementation. First, if a flaw is discovered with hardware-implemented cryptography, the flaw cannot be fixed in most cases without a recall of the product, because hardware is not easily replaceable like software. Second, because the hardware product is expected to work for years, the adversary's computing power will only increase over time.

What an attacker can do

  • Read Application Data (Confidentiality)
  • Modify Application Data (Integrity)
  • Hide Activities (Accountability, Non-Repudiation)

How to prevent it

Architecture and Design

  • When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations. As with all cryptographic mechanisms, the source code should be available for analysis. For example, US government systems require FIPS 140-2 certification. Do not develop custom or private cryptographic algorithms. They will likely be exposed to attacks that are well-understood by cryptographers. Reverse engineering techniques are mature. If the algorithm can be compromised if attackers find out how it works, then it is especially weak. Periodically ensure that the cryptography has not become obsolete. Some older algorithms, once thought to require a billion years of computing time, can now be broken in days or hours. This includes MD4, MD5, SHA1, DES, and other algorithms that were once regarded as strong.
  • Ensure that the design allows one cryptographic algorithm to be replaced with another in the next generation or version. Where possible, use wrappers to make the interfaces uniform. This will make it easier to upgrade to stronger algorithms. With hardware, design the product at the Intellectual Property (IP) level so that one cryptographic algorithm can be replaced with another in the next generation of the hardware product.
  • Carefully manage and protect cryptographic keys (see CWE-320). If the keys can be guessed or stolen, then the strength of the cryptography itself is irrelevant.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Industry-standard implementations will save development time and may be more likely to avoid errors that can occur during implementation of cryptographic algorithms. Consider the ESAPI Encryption feature.

Implementation

  • When using industry-approved techniques, use them correctly. Don't cut corners by skipping resource-intensive steps (CWE-325). These steps are often essential for preventing common attacks.

How to find it

  • Automated Analysis. Automated methods may be useful for recognizing commonly-used libraries or features that have become obsolete.
  • Manual Analysis. This weakness can be detected using tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session.
  • Automated Static Analysis - Binary or Bytecode. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Bytecode Weakness Analysis - including disassembler + source code weakness analysis Binary Weakness Analysis - including disassembler + source code weakness analysis Binary / Bytecode simple extractor - strings, ELF readers, etc.
  • Manual Static Analysis - Binary or Bytecode. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Binary / Bytecode disassembler - then use manual analysis for vulnerabilities & anomalies
  • Dynamic Analysis with Automated Results Interpretation. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Web Application Scanner Web Services Scanner Database Scanners
  • Dynamic Analysis with Manual Results Interpretation. According to SOAR, the following detection techniques may be useful: Highly cost effective: Man-in-the-middle attack tool Cost effective for partial coverage: Framework-based Fuzzer Automated Monitored Execution Monitored Virtual Environment - run potentially malicious code in sandbox / wrapper / virtual machine, see if it does anything suspicious
  • Manual Static Analysis - Source Code. According to SOAR, the following detection techniques may be useful: Highly cost effective: Manual Source Code Review (not inspections) Cost effective for partial coverage: Focused Manual Spotcheck - Focused manual analysis of source
  • Automated Static Analysis - Source Code. According to SOAR, the following detection techniques may be useful: Highly cost effective: Source code Weakness Analyzer Context-configured Source Code Weakness Analyzer
  • Automated Static Analysis. According to SOAR, the following detection techniques may be useful: Cost effective for partial coverage: Configuration Checker
  • Architecture or Design Review. According to SOAR, the following detection techniques may be useful: Highly cost effective: Formal Methods / Correct-By-Construction Cost effective for partial coverage: Inspection (IEEE 1028 standard) (can apply to requirements, design, source code, etc.)

CWE-327 on MITRE's CWE site

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Source: MITRE Common Weakness Enumeration, CWE version 4.19.1. CWE is a trademark of The MITRE Corporation.