Created
August 17, 2018 04:47
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Generating RSA key pairs in DER format
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(in-package :cl-user) | |
(ql:quickload '(:ironclad :asn1)) | |
(defun generate-rsa-key-pair (num-bits) | |
"Same as (ironclad:generate-key-pair :rsa :num-bits num-bits) except returning in DER format." | |
(check-type num-bits integer) | |
(let ((l (floor num-bits 2))) | |
(multiple-value-bind (p q n) | |
(loop for a = (ironclad:generate-prime (- num-bits l)) | |
for b = (ironclad:generate-prime l) | |
for c = (* a b) | |
until (and (/= a b) (= num-bits (ironclad::integer-length c))) | |
finally (return (values a b c))) | |
(let* ((phi (* (1- p) (1- q))) | |
(e (loop for e = (+ 2 (ironclad:strong-random (- phi 2))) | |
until (= 1 (ironclad::gcd e phi)) | |
finally (return e))) | |
(d (ironclad::modular-inverse-with-blinding e phi))) | |
(values (asn1:encode | |
`((:sequence | |
. ((:integer . 0) | |
(:integer . ,n) | |
(:integer . ,e) | |
(:integer . ,d) | |
(:integer . ,p) | |
(:integer . ,q) | |
(:integer . ,(mod d (1- p))) | |
(:integer . ,(mod d (1- q))) | |
(:integer . ,(ironclad::expt-mod q (- p 2) p)))))) | |
(asn1:encode | |
`((:sequence | |
. ((:sequence . ((:object-identifier . #(1 2 840 113549 1 1 1)) | |
(:null))) | |
(:bit-string . ,(asn1:encode | |
`((:sequence . ((:integer . ,n) | |
(:integer . ,e))))))))))))))) |
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