Private Pem

Private Pem
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Aug 20, 2020, 10:00 am EDT
| 3 min read

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PEM is a container file format often used to store cryptographic keys. It’s used for many different things, as it simply defines the structure and encoding type of the file used to store a bit of data.
PEM is just a standard; they contain text, and the format dictates that PEM files start with…
Everything in between is base64 encoded ( uppercase and lowercase letters, digits, + , and / ). This forms a block of data that can be used in other programs. A single PEM file can contain multiple blocks.
This can be used to represent all kinds of data, but it’s commonly used to encode keyfiles, such as RSA keys used for SSH, and certificates used for SSL encryption. The PEM file will tell you what it’s used for in the header; for example, you might see a PEM file start with…
…followed by a long string of data, which is the actual RSA private key.
PEM files are used to store SSL certificates and their associated private keys. Multiple certificates are in the full SSL chain, and they work in this order:
In practice, each certificate is listed in a PEM file, using seperate blocks:
You’ll be given these files from your SSL provider for use in your web server. For example, LetsEncrypt’s certbot generates the following certificates, placed in /etc/letsencrypt/live/your-domain-name/ :
These may also use the .crt extension; if you’ve self-signed a certificate with OpenSSL , you’ll get a CRT file rather than PEM, though the contents will still be the same, and the usage will be the same.
To use your certificates, you’ll have to pass them as parameters for your web server. For nginx, you’ll want to specify the ssl_certificate (the full chain PEM file), and ssl_certificate_key (the RSA private key PEM file), after turning on SSL:
For Apache, setup is largely the same, but you’ll need to use the SSLCertificateFile and SSLCertificateKeyFile directives:
PEM files are also used for SSH. If you’ve ever run ssh-keygen to use ssh without a password, your ~/.ssh/id_rsa is a PEM file, just without the extension.
Most notably, Amazon Web Services gives you a PEM file containing a private key whenever you create a new instance, and you must use this key to be able to SSH into new EC2 instances.
You’ll have to use the -i flag with ssh to specify that you want to use this new key instead of id_rsa :
This will sign you in to the server as normal, but you’ll have to specify this flag each time.
An easier method is to add the private key to your ssh-agent with ssh-add :
However, this doesn’t persist across reboots, so you’ll need to run this command on startup or add it to your macOS keychain.
Of course, you could also always simply append your primary public key to the instance’s ~/.ssh/authorized_keys after you’ve signed in once, but this method should work out of the box for any new instances going forward.
It’s worth noting that you should still lock down your SSH server even if you’re using keys yourself.
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I'm new to security and I'm trying to decode some SSL encrypted communication between my machine and server. I managed to obtain private and public keys
as far as I understand private key is this one:
However, Wireshark requires key to be in .pem format to decode communication, can I somehow convert my keys to this format? If no, then how application which uses those packages decodes them?
The ".PEM format" does not really exist as a standard. This is more "whatever OpenSSL does".
PEM comes from an old failed standard for Privacy Enhanced Mail (that's what the acronym means). These days, "PEM" really means: some text that looks like:
I.e. a header line that starts with ----- and contains the designation of the type of data (e.g. "RSA PRIVATE KEY"); a similar trailer line; and between these two lines, a binary object encoded in Base64 .
For RSA private keys, you will encounter mostly two types of PEM-encoded formats. When the header contains "BEGIN RSA PRIVATE KEY" then this is a RSA private key in the format described by PKCS#1 . When the header says "BEGIN PRIVATE KEY" (without the "RSA") then it uses PKCS#8 , a wrapper format that includes the designation of the key type ("RSA") and the private key itself.
In your case, if you see something that looks like PEM and begins with -----BEGIN RSA PRIVATE KEY----- then it is PEM; just put that in a text file, save it under some name (say "serverkey.pem") and configure Wireshark to use that file as server key. This is described in the Wireshark documentation .
Wireshark will probably not be able to read the file if it is encoded in UTF-16 (what Windows somewhat improperly calls "Unicode"). In UTF-16, each character is encoded over two bytes (or four bytes for some characters like Pahawh Hmong ). If you are using Windows' notepad, upon saving the file, choose the "ANSI" or "UTF-8" encoding.
Knowing the server's private key is not enough to decrypt the data if the client and server use a "DHE" or "ECDHE" cipher suite. If the client and server agree to use such a cipher suite and you still want to intercept the data, then you must make an active attack (a Man-in-the-Middle ) in which you impersonate the server when talking to the client, and the client when talking to the server. This is a lot more work and Wireshark won't help you much there.
Just create a file with a ".pem" extension and try using it.
According to this page , the the private key is stored in a PEM file like you described:
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I am wondering if PEM-files contain both private and public keys? What does "PEM" stand for?
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A PEM file may contain just about anything including a public key, a private key, or both, because a PEM file is not a standard. In effect PEM just means the file contains a base64-encoded bit of data. It is called a PEM file by allusion to the old Privacy-Enhanced Mail standards which preceded S/MIME as a mail security standard. These standards specified the format of various keys and messages in a particular base64 format. See RFC 1421 for example.
Typically a PEM file contains a base64 encoded key or certificate with header and footer lines of the form -----BEGIN ----- and -----END ---- . Over time there have evolved many possibilities for , including private keys, public keys, X509 certificates, PKCS7 data, files containing multiple certificates, files containing both the private key and the X509 certificate, PKCS#10 certificate signing requests, ...
RFC 7468 has been written to document this de facto format.
You can decode your PEM formatted x509 certificate with the following command:
PEM certificate contains public key only or private key only or both.
To understand difference between Public Key Algorithm and Signature Algorithm sections read this (both are public).
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SSL .pem files (concatenated certificate container files), are frequently required for certificate installations when multiple certificates are being imported as one file.

This article contains multiple sets of instructions that walk through various .pem file creation scenarios.

Creating a .pem with the Entire SSL Certificate Trust Chain

Open a text editor (such as wordpad) and paste the entire body of each certificate into one text file in the following order:

Make sure to include the beginning and end tags on each certificate.
The result should look like this:

-----BEGIN CERTIFICATE-----

(Your Primary SSL certificate: your_domain_name.crt)

-----END CERTIFICATE-----

-----BEGIN CERTIFICATE-----

(Your Intermediate certificate: DigiCertCA.crt)

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