(Since you top-posted, I will do so too in this thread)
The certificate does not include the private key, only the public key.
In a real (not test) setup you would use these like this:
1. Use the certificate file alone on any computer to encrypt data using
the"openssl cms" or "openssl pkcs7" command.
2. Use the key file AND the certificate file on the recipient computer
to decrypt data using the "openssl cms" or "openssl pkcs#7" command,
with different options.
To tell the difference between the kinds of PEM files, just look at
the first line in a text viewer such as Windows Notepad or GNU less,
it will say so in nice big friendly letters.
P.S.
The differences between the OpenSSL CMS and PKCS#7 commands and
features have little to do with differences between the CMS and
PKCS#7 standards, it is just that some members of the OpenSSL team
had different ideas about what they wanted the command to do, and
then used two names of the standard to tell their work apart.
On 11/22/2012 12:21 AM, Peter Parker wrote:
Dave,
Thank you for the quick and thorough response. This is good stuff.
Yes, so the files I will be encrypting will be over 100 bytes. I am
aware of the key size requirements - 1028 was only used as a placeholder
for the example commands I provided. Does this mean that I will be able
to use RSA or not?
You lost me with the chaining and AKI stuff. I have no idea what either
of those mean. Does the CMS approach that you suggested address this
issue? In either case, I like the idea of using CMS.
The major reason that I am using the x509 (or originally the ca) utility
is that I want to be able to set begin and end valid dates (-startdate,
-enddate****) for the public and private keys and create certificates as
well. I also want to associate some metadata with them like organization
and locality, for that I am currently using the -subj command.
Am I correct that the large PEM file includes both a public and private
key? If so I should be able to extract them from the PEM and then use
something (rsautl, enc or ...) to encrypt and decrypt the files. After
successfully extracting what I understand to be a public key from the
PEM, I receive this error from the rsautl utility: "unable to load
Public Key. Error in rsautl"
Could you give me some examples of how you would use CMS or, just use
these utilities properly, to achieve what I'm trying to do.
I really appreciate your help.
Thanks,
Peter
On Tue, Nov 20, 2012 at 10:17 PM, Dave Thompson <dthomp...@prinpay.com
<mailto:dthomp...@prinpay.com>> wrote:
>From: owner-openssl-us...@openssl.org
<mailto:owner-openssl-us...@openssl.org> On Behalf Of Peter Parker
>Sent: Tuesday, 20 November, 2012 20:59
>Subject: This is one for the Pros
Not really. This is pretty basic.
>I've been trying to generate a public/private key pair after
>generating the certificates, but OpenSSL keeps giving me an error.
>The commands and the error are below. Thanks.
No you're not; you're generating a CA keypair and cert (directly),
then an application keypair, then an application cert (via CSR).
Which is the (well, a) correct sequence, for one entity.
>Commands
>#openssl req -new -x509 -extensions v3_ca -days 365 -keyout
caKey.pem
>-passout pass:test -out caCert.crt -batch
>#openssl genrsa -out application.pem -passout pass:test -des3 1028
1028 is an unusual size for an RSA key; most folks use power-of-2
based values like 1024 1536 2048. 1024 is presently rather marginal
for security; for example, NIST has it deprecated since the end of
2010, and prohibited after the end of 2013, for US government use.
>#openssl req -new -key application.pem -passin pass:test -out
application.csr -batch
A second req -new -batch generates a CSR with the same DN ...
>#openssl x509 -req -days 365 -in application.csr -CA caCert.crt
-CAcreateserial
>-CAkey caKey.pem -passin:test -out test-key.pem -extensions ssl_cert
... thus this creates a CA-signed cert which appears to be
self-signed,
and will not chain correctly with OpenSSL. If the ssl_cert section
of your
config file (which doesn't exist in the distro file) includes AKI,
other
software that chains primarily by AKI may work, but this is still
incorrect.
This puts the cert in a file named test-key.pem, which is a
misleading name.
>#openssl rsa -in test-key.pem -passin pass:test -out pub-key.pem
-outform
PEM -pubout
And therefore this command, which is not the last one, fails because
you told it to read the privatekey from a file which is a certificate.
application.pem is your privatekey.
>#openssl rsautl -encrypt -inkey pub-key.pem -pubin -in
testfile.txt -out
eFile.ssl
>Error
>"unable to load Private Key" (I receive this after the last command)
Not last.
>The key thing that I am trying to do is to encrypt some files with
the key
>that I generate. I do however want to use the public and private
keys that
>I get out of the PEM file using the x509 (or the ca utilities).
If (any of) your files are larger than about 100 bytes (for 1024-bit
RSA)
you can't use raw RSA; even if they aren't, you can't interoperate
with
properly designed software that doesn't use raw RSA. The conventional
approach is to encrypt the "bulk" data symmetrically with a nonce
key (DEK)
and PK (RSA) encrypt that DEK; there are numerous schemes that do
this,
but the one that OpenSSL supports directly is PKCS7/CMS/SMIME. (CMS
is an
updated Internet version of PKCS7, and SMIME is a simple wrapping of
CMS.)
You can generate and use RSA keys without using certificates (and
without
using the req x509 ca utilities) IF you have a way to "distribute"
them
correctly -- that is, to make sure the "enveloper" always uses a
correct
publickey for the recipient and not a forged, tampered, or
obsolete one.
(And similarly the verifier for a signer.) Most standard schemes
do use
X.509 certs for this purpose, because they are also standard.
Enjoy
Jakob
--
Jakob Bohm, CIO, Partner, WiseMo A/S. http://www.wisemo.com
Transformervej 29, 2730 Herlev, Denmark. Direct +45 31 13 16 10
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