Talk:EVP Signing and Verifying - Revision history

Doru001: /* Clarification required */

2013-06-16T13:04:45Z

Clarification required

2013-06-15T21:16:39Z

Added response to question

2013-06-15T16:52:05Z

Created page with "== Clarification required == Why is if(1 != EVP_DigestSignFinal(mdctx, *sig, slen)) goto err; done two times?"

New page

== Clarification required ==
Why is
if(1 != EVP_DigestSignFinal(mdctx, *sig, slen)) goto err;
done two times?

@@ Line 2: / Line 2: @@
 Why is
    if(1 != EVP_DigestSignFinal(mdctx, *sig, slen)) goto err;
-done two times?
+done two times?--[[User:Doru001|Doru001]] 13:04, 16 June 2013 (UTC)
 ----
@@ Line 9: / Line 9: @@
 --[[User:Matt|Matt]] 21:16, 15 June 2013 (UTC)

← Older revision		Revision as of 21:16, 15 June 2013
Line 3:		Line 3:
	if(1 != EVP_DigestSignFinal(mdctx, *sig, slen)) goto err;		if(1 != EVP_DigestSignFinal(mdctx, *sig, slen)) goto err;
	done two times?		done two times?
		+
		+	----
		+
		+	Good question! I've added some extra code comments to explain it. Basically the first call has a NULL sig parameter to obtain the length of the signature. Memory is then allocated sufficient to hold the sig, and then the sig is obtained in the second call to EVP_DigestSignFinal.
		+
		+	--[[User:Matt\|Matt]] 21:16, 15 June 2013 (UTC)