Calculating the info-hash of a torrent file

by

Make sure you don’t have a newline at the end of the file, you may also want to make sure it ends with an ‘e’.

The info-hash of a torrent file is the SHA-1 hash of the info-section (in bencoded form) from the .torrent file. Essentially you need to decode the file (it’s bencoded) and remember the byte offsets where the content of the value associated with the “info” key begins and end. That’s the range of bytes you need to hash.

For example, if this is the torrent file:

d4:infod6:pieces20:....................4:name4:test12:piece lengthi1024ee8:announce27:http://tracker.com/announcee

You wan to just hash this section:

d6:pieces20:....................4:name4:test12:piece lengthi1024ee

For more information on bencoding, see BEP3.

More Related Contents:

  1. C++ unordered_map using a custom class type as the key
  2. How do I combine hash values in C++0x?
  3. Compile time string hashing
  4. How to specialize std::hash::operator() for user-defined type in unordered containers?
  5. Magic number in boost::hash_combine
  6. How to get the MD5 hash of a file in C++? [closed]
  7. Mismatch Detected for ‘RuntimeLibrary’
  8. C++ – Why is boost::hash_combine the best way to combine hash-values?
  9. Fast String Hashing Algorithm with low collision rates with 32 bit integer [closed]
  10. Choosing between std::map and std::unordered_map [duplicate]
  11. How to hash and compare a pointer-to-member-function?
  12. Objective C: SHA1
  13. What’s a good hash function for English words?
  14. What is the default hash function used in C++ std::unordered_map?
  15. What is the best way to create a sparse array in C++?
  16. Hash an arbitrary precision value (boost::multiprecision::cpp_int)
  17. Hash function for a string
  18. Hashing with SHA1 Algorithm in C#
  19. error for hash function of pair of ints
  20. how to get hash code of a string in c++
  21. SHA1 hashing in SQLite: how?
  22. MD5 hash from file in C++
  23. How do you transform a number to its sign? [closed]
  24. How to print function pointers with cout?
  25. What is the meaning of the term “free function” in C++?
  26. Screen recorder [closed]
  27. c++ array assignment of multiple values
  28. How can I check if a type is an instantiation of a given class template? [duplicate]
  29. Using SFINAE to check for global operator
  30. GCC, stringification, and inline GLSL?

Leave a Comment