Can MD5 Checksums Reliably Detect Changes in Downloaded PDF Files?
Jan 25, 2025 pm 02:11 PM
Question:
When text extraction cannot be performed, it is a challenge to identify the downloaded PDF file. Is the MD5 verification and a reliable solution?
Answer:
Yes, even if the text and modification date cannot be accessed, the MD5 verification and the reliable method of determining whether the file is changed.
Code fragment:In C#, use system.security.cryptography.md5 name space. Calculate the MD5 verification and very simple:
The generated byte array can be compared with the previous version of the MD5 hash to detect any changes.
using (var md5 = MD5.Create())
{
using (var stream = File.OpenRead(filename))
{
return md5.ComputeHash(stream);
}
} Additional prompt:
To show the hash as a string, use BitConverter to convert it into hexadecimal.
- In order to improve efficiency, if you only need to compare hash, avoid using Base64 encoding.
- It is recommended to release MD5 for resource management, although it is not absolutely necessary.
- You can establish a reliable mechanism to monitor file changes by using the MD5 verification to ensure accurate records and maintaining file integrity.
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