Convert .pem to .crt and .key

Question

Can anyone tell me the correct way/command to extract/convert the certificate .crt and private key .key files from a .pem file? I just read they are interchangable, but not how.

Actual inverse of How to get .pem file from .key and .crt files? — minopret
– minopret, Commented Aug 17, 2020 at 3:47
As per @minopret response, you can just change the .pem extension to .crt if the contents is plain text and beings with "-----BEGIN CERTIFICATE-----" — Jono
– Jono, Commented Oct 15 at 7:26

ThiefMaster · Accepted Answer · 2013-08-26 11:15:56Z

876

I was able to convert pem to crt using this:

openssl x509 -outform der -in your-cert.pem -out your-cert.crt

edited Aug 26, 2013 at 11:15

ThiefMaster

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answered Jan 23, 2013 at 16:23

C.B.

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13 Comments

Andron Over a year ago

Using a text editor is not the best approach. To extract the key in PKCS8 form: openssl pkey -in mumble.pem -out mumble-key.pem If the OpenSSL version is older than 1.0.0, to extract the key as an RSA key: openssl rsa -in mumble.pem -out mumble-key.pem

Damien Carol Over a year ago

I tried your command but I had:

unable to load certificate 140584440387400:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: TRUSTED CERTIFICATE

mylord Over a year ago

the key command (openssl pkey -in mumble.pem -out mumble-key.pem) gives this: unable to load key 129051320116880:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:703:Expecting: ANY PRIVATE KEY

Aero Wang Over a year ago

@Andron both pkey and rsa give me Expecting: ANY PRIVATE KEY error.

questionasker Over a year ago

any solution to get key ?

|

evergreen · Accepted Answer · 2016-10-25 19:07:55Z

Converting Using OpenSSL

These commands allow you to convert certificates and keys to different formats to make them compatible with specific types of servers or software.

Convert a DER file (.crt .cer .der) to PEM

openssl x509 -inform der -in certificate.cer -out certificate.pem

Convert a PEM file to DER

openssl x509 -outform der -in certificate.pem -out certificate.der

Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM

openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes You can add -nocerts to only output the private key or add -nokeys to only output the certificates.

Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)

openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt

Convert PEM to CRT (.CRT file)

openssl x509 -outform der -in certificate.pem -out certificate.crt

OpenSSL Convert PEM

Convert PEM to DER

openssl x509 -outform der -in certificate.pem -out certificate.der

Convert PEM to P7B

openssl crl2pkcs7 -nocrl -certfile certificate.cer -out certificate.p7b -certfile CACert.cer

Convert PEM to PFX

openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt

OpenSSL Convert DER

Convert DER to PEM

openssl x509 -inform der -in certificate.cer -out certificate.pem

OpenSSL Convert P7B

Convert P7B to PEM

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer

Convert P7B to PFX

openssl pkcs7 -print_certs -in certificate.p7b -out certificate.cer openssl pkcs12 -export -in certificate.cer -inkey privateKey.key -out certificate.pfx -certfile CACert.cer

OpenSSL Convert PFX

Convert PFX to PEM

openssl pkcs12 -in certificate.pfx -out certificate.cer -nodes

Generate rsa keys by OpenSSL

Using OpenSSL on the command line you’d first need to generate a public and private key, you should password protect this file using the -passout argument, there are many different forms that this argument can take so consult the OpenSSL documentation about that.
```
openssl genrsa -out private.pem 1024 
```
This creates a key file called private.pem that uses 1024 bits. This file actually have both the private and public keys, so you should extract the public one from this file:
```
openssl rsa -in private.pem -out public.pem -outform PEM -pubout or openssl rsa -in private.pem -pubout > public.pem or openssl rsa -in private.pem -pubout -out public.pem 
```
You’ll now have public.pem containing just your public key, you can freely share this with 3rd parties. You can test it all by just encrypting something yourself using your public key and then decrypting using your private key, first we need a bit of data to encrypt:
Example file :
```
echo 'too many secrets' > file.txt 
```
You now have some data in file.txt, lets encrypt it using OpenSSL and the public key:
```
openssl rsautl -encrypt -inkey public.pem -pubin -in file.txt -out file.ssl 
```
This creates an encrypted version of file.txt calling it file.ssl, if you look at this file it’s just binary junk, nothing very useful to anyone. Now you can unencrypt it using the private key:
```
openssl rsautl -decrypt -inkey private.pem -in file.ssl -out decrypted.txt 
```
You will now have an unencrypted file in decrypted.txt:
```
cat decrypted.txt |output -> too many secrets 
```

RSA TOOLS Options in OpenSSL

NAME

rsa - RSA key processing tool
SYNOPSIS

openssl rsa [-help] [-inform PEM|NET|DER] [-outform PEM|NET|DER] [-in filename] [-passin arg] [-out filename] [-passout arg] [-aes128] [-aes192] [-aes256] [-camellia128] [-camellia192] [-camellia256] [-des] [-des3] [-idea] [-text] [-noout] [-modulus] [-check] [-pubin] [-pubout] [-RSAPublicKey_in] [-RSAPublicKey_out] [-engine id]
DESCRIPTION

The rsa command processes RSA keys. They can be converted between various forms and their components printed out. Note this command uses the traditional SSLeay compatible format for private key encryption: newer applications should use the more secure PKCS#8 format using the pkcs8 utility.
COMMAND OPTIONS
```
-help 
```
Print out a usage message.
```
-inform DER|NET|PEM 
```
This specifies the input format. The DER option uses an ASN1 DER encoded form compatible with the PKCS#1 RSAPrivateKey or SubjectPublicKeyInfo format. The PEM form is the default format: it consists of the DER format base64 encoded with additional header and footer lines. On input PKCS#8 format private keys are also accepted. The NET form is a format is described in the NOTES section.
```
-outform DER|NET|PEM 
```
This specifies the output format, the options have the same meaning as the -inform option.
```
-in filename 
```
This specifies the input filename to read a key from or standard input if this option is not specified. If the key is encrypted a pass phrase will be prompted for.
```
-passin arg 
```
the input file password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl.
```
-out filename 
```
This specifies the output filename to write a key to or standard output if this option is not specified. If any encryption options are set then a pass phrase will be prompted for. The output filename should not be the same as the input filename.
```
-passout password 
```
the output file password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl.
```
-aes128|-aes192|-aes256|-camellia128|-camellia192|-camellia256|-des|-des3|-idea 
```
These options encrypt the private key with the specified cipher before outputting it. A pass phrase is prompted for. If none of these options is specified the key is written in plain text. This means that using the rsa utility to read in an encrypted key with no encryption option can be used to remove the pass phrase from a key, or by setting the encryption options it can be use to add or change the pass phrase. These options can only be used with PEM format output files.
```
-text 
```
prints out the various public or private key components in plain text in addition to the encoded version.
```
-noout 
```
this option prevents output of the encoded version of the key.
```
-modulus 
```
this option prints out the value of the modulus of the key.
```
-check 
```
this option checks the consistency of an RSA private key.
```
-pubin 
```
by default a private key is read from the input file: with this option a public key is read instead.
```
-pubout 
```
by default a private key is output: with this option a public key will be output instead. This option is automatically set if the input is a public key.
```
-RSAPublicKey_in, -RSAPublicKey_out 
```
like -pubin and -pubout except RSAPublicKey format is used instead.
```
-engine id 
```
specifying an engine (by its unique id string) will cause rsa to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms.
NOTES

The PEM private key format uses the header and footer lines:
```
-----BEGIN RSA PRIVATE KEY----- -----END RSA PRIVATE KEY----- 
```
The PEM public key format uses the header and footer lines:
```
-----BEGIN PUBLIC KEY----- -----END PUBLIC KEY----- 
```
The PEM RSAPublicKey format uses the header and footer lines:
```
-----BEGIN RSA PUBLIC KEY----- -----END RSA PUBLIC KEY----- 
```
The NET form is a format compatible with older Netscape servers and Microsoft IIS .key files, this uses unsalted RC4 for its encryption. It is not very secure and so should only be used when necessary.

Some newer version of IIS have additional data in the exported .key files. To use these with the utility, view the file with a binary editor and look for the string "private-key", then trace back to the byte sequence 0x30, 0x82 (this is an ASN1 SEQUENCE). Copy all the data from this point onwards to another file and use that as the input to the rsa utility with the -inform NET option.

EXAMPLES

To remove the pass phrase on an RSA private key:
```
 openssl rsa -in key.pem -out keyout.pem 
```
To encrypt a private key using triple DES:
```
 openssl rsa -in key.pem -des3 -out keyout.pem 
```
To convert a private key from PEM to DER format:
```
 openssl rsa -in key.pem -outform DER -out keyout.der 
```
To print out the components of a private key to standard output:
```
 openssl rsa -in key.pem -text -noout 
```
To just output the public part of a private key:
```
 openssl rsa -in key.pem -pubout -out pubkey.pem 
```
Output the public part of a private key in RSAPublicKey format:
```
 openssl rsa -in key.pem -RSAPublicKey_out -out pubkey.pem 
```

Still this does not answer the question which is how to get the private key from the (exported) binary certificate.
thank you, wondering if I have a PEM containing a private key and certificates, how can I get certificates only? I know I can copy the certificates part from it using text editor, but I want to know is there any openssl command, thanks

Highway of Life · Accepted Answer · 2018-02-17 00:46:53Z

To extract the key and cert from a pem file:

Extract key

openssl pkey -in foo.pem -out foo.key

Another method of extracting the key...

openssl rsa -in foo.pem -out foo.key

Extract all the certs, including the CA Chain

openssl crl2pkcs7 -nocrl -certfile foo.pem | openssl pkcs7 -print_certs -out foo.cert

Extract the textually first cert as DER

openssl x509 -in foo.pem -outform DER -out first-cert.der

openssl x509 -outform der -in C:\Users\Greg\.ssh\e360_stork_listener.pem -out C:\Users\Greg\.ssh\e360_stork_listener.crt unable to load certificate 4294956672:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:708:Expecting: TRUSTED CERTIFICATE
@user3217883 For that error see if this helps: stackoverflow.com/questions/20837161/…

Saikat · Accepted Answer · 2025-01-15 20:33:22Z

Pre-requisite

OpenSSL should be installed. If Git Bash is installed on Windows, try that! Alternate binaries can be found here.

Step 1: Extract `.key` from `.pem`

openssl pkey -in cert.pem -out cert.key

Step 2: Extract `.crt` from `.pem`

openssl x509 -outform PEM -in cert.pem -out cert.crt

I get empty file but no error in console for .crt file command. Any idea?
Sorry, @Sisir no clue about that. Feel free to create a new post describing your issue.

Asmtony · Accepted Answer · 2021-02-14 11:04:40Z

This is what I did on windows.

Download a zip file that contains the open ssl exe from Google
Unpack the zip file and go into the bin folder.
Go to the address bar in the bin folder and type cmd. This will open a command prompt at this folder.
move/Put the .pem file into this bin folder.
Run two commands. One creates the cert and the second the key file

openssl x509 -outform der -in yourPemFilename.pem -out certfileOutName.crt openssl rsa -in yourPemFilename.pem -out keyfileOutName.key

"Go to the address bar in the bin folder and type cmd" this is the coolest windows trick I have ever seen :D
this worked for me openssl x509 -outform der -in a.pem -out a.crt

Barney Szabolcs · Accepted Answer · 2019-11-08 10:13:21Z

If you asked this question because you're using mkcert then the trick is that the .pem file is the cert and the -key.pem file is the key.

(You don't need to convert, just run mkcert yourdomain.dev otherdomain.dev )

Gerard ONeill · Accepted Answer · 2019-09-06 01:30:19Z

A .crt stores the certificate.. in pem format. So a .pem, while it can also have other things like a csr (Certificate signing request), a private key, a public key, or other certs, when it is storing just a cert, is the same thing as a .crt.

A pem is a base 64 encoded file with a header and a footer between each section.

To extract a particular section, a perl script such as the following is totally valid, but feel free to use some of the openssl commands.

 perl -ne "\$n++ if /BEGIN/; print if \$n == 1 && /BEGIN/.../END/;" mydomain.pem

where ==1 can be changed to which ever section you need. Obviously if you know exactly the header and footer you require and there is only one of those in the file (usually the case if you keep just the cert and the key in there), you can simplify it:

 perl -ne "print if /^-----BEGIN CERTIFICATE-----\$/.../END/;" mydomain.pem

Carlos · Accepted Answer · 2024-07-19 22:36:23Z

.pem and .crt are just plain text that is interpreted by the server as an SSL certificate, consists of two parts the key and the certificate.

Start by checking the compatibility of them by running

openssl rsa -noout -modulus -in test.key | openssl md5 openssl x509 -noout -modulus -in test.crt | openssl md5

the output of this must match like

(stdin)= 643bd39250bdce26c0ff3958cab0c9cc (stdin)= 643bd39250bdce26c0ff3958cab0c9cc

if does not match observe that the .pem/.crt file might contain several certificates, something like:

separate it and test every one of the sections on a different file with a .pem/.crt extension. the section that matches should be the one on top of the list, or you can just use that section in your certificate.

you can check a further explanation on this article https://carloshdelreal.medium.com/debugging-an-ssl-certificate-b030d330aaa8

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Pre-requisite

Step 1: Extract `.key` from `.pem`

Step 2: Extract `.crt` from `.pem`

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Extract key

Extract all the certs, including the CA Chain

Extract the textually first cert as DER

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Pre-requisite

Step 1: Extract .key from .pem

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Step 1: Extract `.key` from `.pem`

Step 2: Extract `.crt` from `.pem`