SHA-1 Hash Generator

Calculate the legacy SHA-1 digest of UTF-8 text for compatibility checks; SHA-1 is collision-broken and should not protect new security-sensitive data.

Description

Calculate the 160-bit SHA-1 digest of UTF-8 text and display it as 40 lowercase hexadecimal characters.

SHA-1 is a one-way hash function in the Secure Hash Standard. The tool encodes entered text as UTF-8, hashes those bytes, and returns a fixed 160-bit digest. A tiny input change normally produces a completely different digest, but hashing does not encrypt the text and cannot be reversed to recover it.^[1]

When to use SHA-1 Hash Generator

Use SHA-1 when a protocol, API, checksum manifest, content-addressed identifier, or test vector specifies that exact algorithm. SHA-1 is collision-broken and retained only for compatibility.

How SHA-1 Hash Generator works

SHA-1 pads the UTF-8 byte sequence, divides it into fixed-size blocks, expands each block into a message schedule, and repeatedly mixes that schedule with a fixed internal state. The final state is serialized as the 160-bit digest.^{[2, 1]}

How the SHA-1 hashing function processes input

Encode the entered Unicode text as UTF-8 bytes.
Append SHA padding and the original message length.
Process every padded block with the SHA-1 compression function and constants.
Render the resulting 20 bytes as 40 lowercase hexadecimal characters.

Limitations and assumptions

SHA-1 collision resistance is broken and NIST has deprecated it for security-sensitive uses.
Equal digests are useful evidence that bytes match, but a bare hash does not authenticate the source.
Hashes are unsuitable for password storage without a deliberately slow, salted password-hashing construction.
Whitespace, normalization, line endings, and character encoding all change the byte sequence and therefore the digest.

Alternative or Complementary approaches

Use SHA-256 or a stronger SHA-2/SHA-3 algorithm for new designs. Use HMAC when a shared secret must authenticate the message.

References

Encoding Standard — WHATWG
FIPS 180-4: Secure Hash Standard — National Institute of Standards and Technology

Similar or alternative tools

SHA-256 Hash Generator
Calculate a SHA-2 digest with a different output size.
MD5 Hash Generator
Check legacy MD5 values while accounting for its security limitations.
CRC-32 Checksum
Use a fast checksum when only accidental corruption is in scope.