SHA256Sum Calculator
Generate SHA256 Checksums for Files
The sha256sum command is a powerful utility for computing and verifying SHA256 hashes (checksums) of files. This is crucial for ensuring data integrity and detecting any accidental corruption or malicious tampering during file transfer or storage.
# To compute the SHA256 hash (checksum) of a file:
sha256sum <file>Compute SHA256 Hash from Input Text
You can also compute the SHA256 hash directly from standard input. This is useful for hashing text strings or piped output from other commands.
# To compute hash (checksum) from input text:
# Enter text in keyboard and finish by ctrl-D at beginning of line
sha256sum
Some text
^D
# Alternatively, using echo for a single line:
echo -n "Hello World" | sha256sumVerify SHA256 Checksums
The sha256sum --check option allows you to verify if the computed checksums of files match a provided checksum file. This is the primary method for confirming data integrity.
# To verify if a hash (checksum) is correct using a hash-file:
# sha256sum will process each entry in <file-with-list-of-checksums>.
# It checks if the file exists, computes its checksum, and compares it
# with the hash provided in the file.
# Output: "filename: OK" for matches, "filename: FAILED" for mismatches.
sha256sum --check <file-with-list-of-checksums>
# To verify checksums while ignoring missing files:
# This is useful to check for tampered files without being alerted about
# files that are simply not present.
sha256sum --check --ignore-missing <file-with-list-of-checksums>Understanding SHA256 Checksums
SHA256 (Secure Hash Algorithm 256-bit) is a cryptographic hash function that produces a fixed-size 256-bit (64 hexadecimal characters) hash value. Even a tiny change in the input data will result in a completely different hash value, making it highly effective for detecting modifications.
Use Cases for SHA256Sum
- File Integrity Verification: Ensure downloaded files are not corrupted or altered.
- Software Distribution: Provide checksums alongside software downloads for users to verify.
- Data Storage: Maintain checksums to detect data degradation over time.
- Security Audits: Confirm that critical system files have not been modified.