Okay, I need to write a professional Wikipedia-style document in Korean about "Collision Attack" under category of technology, specifically security and protection. Let me start by understanding what a collision attack is

First, the document structure have a title (H1), an overview/introduction section, several detailed sections ( H2 and H3 and maybe a references or related documents section. The needs to be accurate, objective with appropriate depth and easy to understand Also, use markdown formatting with proper heading hierarchy, lists, tables, and code blocks if necessary. The length should be over 800 characters, which is manageable since the user wants a detailed explanation.

Starting with the title, it's given as "충돌 공격" so that's straightforward. The overview should explain what a collision attack is simple terms. I should mention cryptographic hash functions and how a collision happens when two inputs produce the same hash output. Then, the introduction should set the context in data, why hash functions are important, and how collisions can be exploited.

Next, detailed sections. Let me break it down. Maybe start with the basic concept of collision attacks, explaining hash functions and the birthday problem. Then, types of collision attacks: maybe free-start, chosen-prefix, and identical-prefix. Each type needs a brief explanation. Then, implications and applications—how these attacks affect real-world systems like digital signatures, SSL certificates, blockchain. Examples would be the MD5 and SHA-1 collisions.

After that, prevention and countermeasures. Discuss using secure hash algorithms like SHA-256, salting in password storage, regular algorithm updates, and collision-resistant designs. Then, related concepts like preimage attacks and second preimage attacks, explaining the differences.

I should also include a section on the history of collision attacks, mentioning when MD5 and SHA-1 were broken, the research efforts involved. Maybe the Stevens et al. work on SHA-1.

Need to ensure that technical terms are explained. For example, when talking about the birthday problem, I should briefly explain that it's a probability theory concept that makes finding collisions easier than brute force. Also, terms like "identical-prefix" might need a simple explanation.

In terms of formatting, use H1 for the title, H2 for each main section, H3 if needed. Use bullet points for types of attacks and countermeasures. Maybe a table comparing different hash functions and their vulnerability. Also, code blocks if showing examples of hash collisions, but since it's theoretical, maybe not necessary. Instead, just describe the examples.

Check for accuracy: Make sure that the examples of MD5 and SHA-1 are correct. Stevens et al. did a practical attack on SHA-1 in 2017. Also, note that SHA-2 and SHA-3 are currently considered secure.

Potential pitfalls: Don't confuse collision attacks with other types of attacks like preimage attacks. Need to clearly differentiate them. Also, ensure that the explanation of the birthday attack is accurate, mentioning that it reduces the computational effort needed to find collisions.

Length: Each section should have enough detail. The overview might be a paragraph, each H2 section a few paragraphs. Let me estimate the characters. In Korean, each character is a letter, so 800 characters would be about 2-3 paragraphs in English. But since the user wants a thorough document, I'll aim for more.

Now, structuring the document:

1. 제목 (H1)
2. 개요/소개
3. 충돌 공격의 개념
4. 해시 함수와 충돌
5. 생일 문제와 충돌 가능성
6. 충돌 공격의 유형
7. 자유 시작 충돌
8. 선택적 접두사 충돌
9. 동일 접두사 충돌
10. 영향 및 실제 사례
11. 디지털 서명 위조
12. SSL 인증서 문제
13. 블록체인 관련 위험
14. 예방 및 대응 방안
15. 강력한 해시 알고리즘 사용
16. 솔트 적용
17. 정기적 알고리즘 업데이트
18. 관련 개념
19. 사전 이미지 공격
20. 두 번째 사전 이미지 공격
21. 역사적 배경
22. MD5, SHA-1 취약점 발견
23. 참고 자료

Make sure each section flows logically. Use bold for technical terms when first introduced, and explain them. For example, when mentioning 해시 충돌, explain it's when two different inputs have the same output hash.

In the prevention section, mention specific algorithms like SHA-256, SHA-3, and why they are more secure. Discuss how salting adds randomness to prevent precomputed attacks. Also, note that even secure algorithms can become vulnerable over time as computational power increases.

In the examples, clarify how an attacker could create two documents with the same hash. For instance, creating a legitimate and a malicious document with the same MD5 hash, leading to signature forgery. The Flame malware used this technique.

Need to check for any inaccuracies. For example, the difference between collision attacks and birthday attacks. The birthday attack is a method to find collisions, but collision attacks are the broader concept. Also, ensure that the explanation of the birthday problem is concise.

I should also mention that collision resistance is a required property for cryptographic hash functions, and when it's broken, the algorithm is considered insecure. This leads to the need for transitioning to more secure algorithms.

In the history section, note that MD5 collisions were first demonstrated in 2004, and SHA-1 in 2017. Mention the cost and resources required for these attacks, showing the practical feasibility over time.

Now, translating all this into Korean, making sure the terms are correctly used. Use markdown syntax appropriately. Avoid markdown in the content descriptions here, but in the final document, structure it properly.

Potential table: Maybe a comparison table of hash functions and their collision status. For example:

Including this would help readers quickly grasp the information.

Also, in the implications section, explain how digital signatures rely on hash uniqueness. If two documents hash to the same value, a signature on one is valid for the other, leading to forgery. SSL certificates could be impersonated if hashes collide, leading to man-in-the-middle attacks.

For blockchain, if a hash function used in the blockchain is vulnerable, it could allow double-spending or block tampering. However, most blockchains use SHA-256, which is still secure.

In the prevention section, mention that even if a collision is found, the system's design should detect and handle it, like using HMAC or digital signature schemes that include additional data.

I think that covers the main points. Now, structure all this into the markdown document, ensuring clarity and meeting the user's requirements.