Private Key Pem

Private Key Pem

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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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In public-key cryptography, also known as asymmetric cryptography , the encryption mechanism relies upon two related keys, a public key and a private key. The public key is used to encrypt the message, while only the owner of the private key can decrypt the message.
In this tutorial, we’ll learn how to read public and private keys from a PEM file.
First, we’ll study some important concepts around public-key cryptography. Then we’ll learn how to read PEM files using pure Java.
Finally, we’ll explore the BouncyCastle library as an alternate approach.
Before we start, let’s discuss some key concepts.
X.509 is a standard defining the format of public-key certificates. So this format describes a public key, among other information.
DER is the most popular encoding format to store data, like X.509 certificates, and PKCS8 private keys in files. It's a binary encoding, and the resulting content can't be viewed with a text editor.
PKCS8 is a standard syntax for storing private key information. The private key can be optionally encrypted using a symmetric algorithm.
Not only can RSA private keys be handled by this standard, but also other algorithms. The PKCS8 private keys are typically exchanged through the PEM encoding format.
PEM is a base-64 encoding mechanism of a DER certificate. PEM can also encode other kinds of data, such as public/private keys and certificate requests.
A PEM file also contains a header and footer describing the type of encoded data:
Let’s start by reading the PEM file, and storing its content into a string:
Now we'll build a utility method that gets the public key from the PEM encoded string:
Let’s suppose we receive a File as a parameter:
As we can see, first we need to remove the header, the footer, and the new lines as well. Then we need to decode the Base64-encoded string into its corresponding binary format.
Next, we need to load the result into a key specification class able to handle public key material. In this case, we'll use the X509EncodedKeySpec class.
Finally, we can generate a public key object from the specification using the KeyFactory class.
Now that we know how to read a public key, the algorithm to read a private key is very similar.
We'll use a PEM encoded private key in PKCS8 format. Let's see what the header and footer look like:
As we learned previously, we need a class able to handle PKCS8 key material. The PKCS8EncodedKeySpec class fills that role.
We'll explore the BouncyCastle library, and see how we can use it as an alternative to the pure Java implementation.
There are a few important classes that we need to be aware of when using BouncyCastle:
Let's see another approach that wraps Java's classes ( X509EncodedKeySpec, KeyFactory ) into BouncyCastle's own class ( JcaPEMKeyConverter ):
Now we'll see two examples that are very similar to the ones shown above.
In the first example, we just need to replace the X509EncodedKeySpec class with the PKCS8EncodedKeySpec class, and return a RSAPrivateKey object instead of a RSAPublicKey :
Now let's rework the second approach from the previous section a bit in order to read a private key:
As we can see, we just replaced SubjectPublicKeyInfo with PrivateKeyInfo and RSAPublicKey with RSAPrivateKey .
There are a couple of advantages provided by the BouncyCastle library.
One advantage is that we don’t need to manually skip or remove the header and footer. Another is that we’re not responsible for the Base64 decoding, either. Therefore, we can write less error-prone code with BouncyCastle.
Moreover, the BouncyCastle library supports the PKCS1 format as well. Despite the fact that PKCS1 is also a popular format used to store cryptographic keys (only RSA keys), Java doesn't support it on its own.
In this article, we learned how to read public and private keys from PEM files.
First, we studied a few key concepts around public-key cryptography. Then we saw how to read public and private keys using pure Java.
Finally, we explored the BouncyCastle library and discovered it’s a good alternative, since it provides a few advantages compared to the pure Java implementation.
The full source code for both the Java and BouncyCastle approaches is available over on GitHub.

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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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How do I generate a private key from a .PEM file?
Top 5 user and mod at https://crypto.stackexchange.com/ · Author has 533 answers and 413.8K answer views · 1 y ·
How do you generate a PEM file from a private key?
How do I generate a private key from a PEM file using PuttyGen?
How do I extract a private key from PEM?
How do you create a PEM file from a public key?
I have a bitcoin address but no private key. how do I generate a private key?
Author has 3.3K answers and 1.1M answer views · 2 y ·
How do you generate a PEM file from a private key?
How do I generate a private key from a PEM file using PuttyGen?
How do I extract a private key from PEM?
How do you create a PEM file from a public key?
I have a bitcoin address but no private key. how do I generate a private key?
How do you extract a public key from a PEM file?
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What is the difference between a private key and a secret key?
How do I read a PEM public and private key?
How do I make my public key a private key?
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How do you generate a PEM file from a private key?
How do I generate a private key from a PEM file using PuttyGen?
How do I extract a private key from PEM?
How do you create a PEM file from a public key?
I have a bitcoin address but no private key. how do I generate a private key?
How do you extract a public key from a PEM file?
How do I generate a private key from my bitcoin address?
What is the difference between a private key and a secret key?
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PEM stands for Privacy Enhanced Mail. It is used for cryptographic content because cryptographic content is generally binary. Mail however is a text based protocol, so it needs some kind of way to encode the binary data needed for cryptography. The PEM encoding is therefore also sometimes referred to as “ASCII armor” as it protects the binary data from being altered during the processing of the text.
PEM stands for Privacy Enhanced Mail. It is used for cryptographic content because cryptographic content is generally binary. Mail however is a text based protocol, so it needs some kind of way to encode the binary data needed for cryptography. The PEM encoding is therefore also sometimes referred to as “ASCII armor” as it protects the binary data from being altered during the processing of the text.
A PEM encoded file may contain any kind of data, just like XML or HTML may contain any kind of data. PEM is not just for encoding private keys.
Private keys may be encoded in two distinct ways. Quite often the private key uses the inner-encoding defined in PKCS #8. This encoding does not just contain the private key, but also the type of key within the encoding. This type is therefore left out of the label, which is just “PRIVATE KEY”. This type is commonly preferred.
The other way is that the private key is encoded only as it is defined in a specific standard. For instance, RSA private keys are encoded using the PKCS #1-defined structure. In that case the type is within the header field, which then reads “RSA PRIVATE KEY”. It could also read “EC PRIVATE KEY” in which case the content is encoded using X9.62 defined structure.
Finally, to top it all of, the PEM structure may contain an encrypted private key which is then encoded. In that case the additional lines, item 2 in above list, needs to be present.
In all cases the structure of the private key is defined using the ASN.1 language. The actual private key values are then encoded using BER/DER encoding.
To decode (or “parse” but not “generate”) a private key from PEM you need:
Longer answer is that puttyGen can’t create a new key from a PEM, but it *can* convert one if one is present. look in the pem for a line like this:
if it is present, this means there is a private key in the file, and you can convert it to a puTTY key by “Import Key” on the conversions menu.
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