Is a hmac-sha1 hash always 20 bytes long? Python code

Question

Is the digest always 20 bytes long? len(hashed.digest()) seems to always be 20.

hashed = hmac.new(key, signature_base_string, sha)
print hashed.digest()
print len(hashed.digest())
i = 0
for c in hashed.digest():
    i = i + 1
    print ord(c)
print base64.b64encode(hashed.digest())

[yes it is](https://secure.wikimedia.org/wikipedia/en/wiki/Sha1) — President James K. Polk, Jul 30 '11 at 01:34

score 11 · Answer 1 · answered Jul 30 '11 at 01:35

11

All hashing functions have fixed length outputs. SHA1 is 160 bits, or 20 bytes.

answered Jul 30 '11 at 01:35

Keith

42,110
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score 2 · Answer 2 · answered Jul 30 '11 at 01:35

2

Yes. SHA1 HMAC hash is always 160 bits (e.g. 20 bytes).

answered Jul 30 '11 at 01:35

MByD

135,866
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score 2 · Answer 3 · answered Jul 30 '11 at 01:37

2

SHA-1 always returns 160 bits, or 20 bytes.

http://www.itl.nist.gov/fipspubs/fip180-1.htm

"For a message of length < 2^64 bits, the SHA-1 produces a 160-bit condensed representation of the message called a message digest."

answered Jul 30 '11 at 01:37

Joe

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Is a hmac-sha1 hash always 20 bytes long? Python code

3 Answers3