sha224-final

Arguments: context &key return

Finalize and return the SHA224 hash from context in a format determined by the return keyword argument.

return can be one of the following values:

• :integer (the default): the return value is an integer of up to 128 bits representing the digest. Warning: note that an integer representation of the digest potentially loses information if the generated signature has leading octets containing only zeroes. Care should be taking when using this return type if you intend to further encode the signature (such as to a base64-encoded string). See the example below.
• :usb8: return an (unsigned-byte 8) array containing the digest.
• :hex: return a string containing the hexadecimal representation of the digest. See hex-string-to-integer.

cl-user(4): (setq c (sha224-init))
#S(excl::md-context :ctx 9183104 :size 28)
cl-user(5): (sha224-update c "foo")
cl-user(6): (sha224-final c :return :usb8)
#(8 8 246 78 96 213 137 121 252 182 ...)

;;  Potential problem with :return :integer (or :return unspecified
;;  as the default is :integer). The call is to SHA224-FILE which calls
;;  SHA224-FINAL and returns the value SHA224-FINAL returns.
;;
;;  Here we get the sha224 value in a shell:
% openssl dgst -sha224 -hex uninstall.jpg 
SHA224(uninstall.jpg)= 012d03e402813fa87201182a9fa8dc71d5662e07a3298e6e3fee902a

;; Now we get it with SHA224-FILE:
cl-user(17): (sha224-file "~/uninstall.jpg")
123830469993168619693673182033704503020973917482279183198628778026
cl-user(18): (format t "~x" *)
12d03e402813fa87201182a9fa8dc71d5662e07a3298e6e3fee902a
nil
cl-user(19): 

;; Note the hex values are the same but the leading 0 is not printed
;; by Lisp, which is dealing with the value as an integer. The leading
;; 0 is preserved when the :return is :hex:
cl-user(21): (sha224-file "~/unistall.jpg" :return :hex)
"012d03e402813fa87201182a9fa8dc71d5662e07a3298e6e3fee902a"
cl-user(22): 

See MD*, SHA*, HMAC, and other message digest support in miscellaneous.htm. See also digest-final.

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This page was not revised from the 10.0 page.
Created 2019.8.20.