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CWE-327

壊れた、あるいは危険な暗号アルゴリズムの使用

Use of a Broken or Risky Cryptographic Algorithm
脆弱性 レビュー中
JA

その製品は、壊れた、または危険な暗号アルゴリズムやプロトコルを使用しています。

暗号アルゴリズムは、不正な行為者による観察や影響を防ぐためにデータをスクランブルする方法である。安全でない暗号を悪用することで、機密情報の暴露、予期しない方法でのデータの変更、他のユーザーやデバイスのなりすまし、その他の影響を与えることができます。

安全なアルゴリズムを作成することは非常に難しく、熟練した暗号専門家による有名なアルゴリズムでさえ破られています。様々な種類の暗号を破ったり弱めたりするよく知られたテクニックが存在する。従って、ほとんどの製品で使用されるべき、よく理解され研究された少数のアルゴリズムが存在する。非標準的なアルゴリズムや既知の安全でないアルゴリズムを使用することは、決意のある敵対者がそのアルゴリズムを破り、保護されているデータを侵害することができる可能性があるため危険である。

暗号技術の進歩は非常に速いため、あるアルゴリズムがかつて強力だと考えられていたとしても、「安全ではない」とみなされることはよくあることです。これは、新たな攻撃が発見された場合や、計算能力が大幅に向上し、暗号アルゴリズムが当初考えられていたほどの保護を提供できなくなった場合に起こり得る。

多くの理由から、ソフトウェア実装とは対照的に、暗号アルゴリズムをハードウェアで展開する場合、この弱点の管理はさらに難しくなる。第一に、ハードウェアで実装された暗号に欠陥が発見された場合、ハードウェアはソフトウェアのように簡単に交換できないため、ほとんどの場合、製品のリコールなしに欠陥を修正することはできません。第二に、ハードウェア製品は何年も機能することが予想されるため、敵の計算能力は時間の経過とともに増大する一方である。

EN

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

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.

Scope: Confidentiality / Impact: Read Application Data
Scope: Integrity / Impact: Modify Application Data
Scope: Accountability, Non-Repudiation / Impact: Hide Activities
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 [REF-1192].

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. [REF-267]
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 [REF-1482].

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.
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.
MITRE公式ページ — CWE-327