Building OpenSSL

Michael Wojcik Michael.Wojcik at
Thu Sep 12 19:33:28 UTC 2019

> From: openssl-users [mailto:openssl-users-bounces at] On Behalf Of Osman Zakir
> Sent: Thursday, September 12, 2019 13:45

> I tried enabling both MD2 and RC5

Your previous note said "RC5 or MD4". Are you talking about MD2 or MD4?

> but I got linker errors when trying to build:

How did you "enable" them? If you reconfigured, did you do a "make clean" afterward before trying to build?

> How do I know whether to enable RC5 or MD4, though?

That depends on the needs of your application(s).

> Which one do I enable?  Sorry if this is a stupid question.

Neither. Either. Both. (All, since there seems to be some MD2/MD4 confusion here.) It depends entirely on what you're building OpenSSL for. You haven't told us, so we have no way of answering your question.

Most people have no need for MD2, MD4, or RC5.

>  And what's "afalg" (in "test_afalf")?

AF_ALG is a Linux network address family for userland access to the kernel cryptography subystem. OpenSSL's afalg is (I believe) an engine (i.e. an OpenSSL plugin) that lets OpenSSL use AF_ALG for some cryptographic operations. It's similar in purpose to several of the other engines, such as capi (interface to Windows Crypto API) and pkcs11 (interface to crypto hardware supporting the PKCS#11 standard). If that doesn't answer your question, then you probably don't need to know about it.

Michael Wojcik
Distinguished Engineer, Micro Focus

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