The SHA algorithm produces a hash value of length 160 bits (= 20 bytes).
Based on SHA the slightly modified SHA-1 arose. Both hashing methods were published in 1991 by the U.S. National Institute of Standards and Technology (NIST).
Meanwhile NIST defined 3 new variants of the hash function SHA-1, which create hash values of the length 256, 384 and 512 bits.
Using such long hash values the birthday-attack will probably be prevented successfully for years (see menu Analysis \ Hash \ Attack on the hash value of the digital signature).