Privacy-Enhanced Mail (.PEM)

wikipedia:PEM extension for X.509 certificates. .pem defined in RFCs 1421 through 1424, this is a container format that may include just the public certificate (such as with Apache installs, and CA certificate files /etc/ssl/certs/), or may include an entire certificate chain including public key, private key and root certificates. Confusingly, it may also encode a CSR (e.g. as used here) as the PKCS10 format can be translated into PEM. The name is from Privacy Enhanced Mail (PEM), a failed method for secure email but the container format it used lives on, and is a base64 translation of the x509 ASN.1 keys.

PEM or DER or PFX

• ssh-keygen -m PEM -t rsa -f your_new_rsa_key.pem

• Convert from .cer to .pem

Read certificate:

• openssl x509 -in certificate.pem -text
• openssl s_client -showcerts -connect YOUR_DOMAIN.COM:443
• keytool -printcert -file certificate.pem

Generate certificate:

• openssl req

PKCS7 chain in DER format. These files also may be named with a .p7b extension

• OpenSSH 7.8, (August 2018) Incompatible changes: ssh-keygen write OpenSSH format private keys by default instead of using OpenSSL's PEM format.

file your_pem_file.pem
your_pem_file.pem PEM RSA private key

file example.org.csr
example.org.csr: PEM certificate request

file your_cert_for_development.cer
your_cert_for_development.cer: Certificate, Version=3

Related terms

• .cer
• X.509
• ssh-keygen -m and openssl req
• .crt (Core FTP)
• .key (Core FTP)
• Let's Encrypt: certbot certonly, certbot certificates
• Nginx ssl_certificate directive
• .pfx or .p12
• IdentityFile

Activities

• Read about certificate extensions: https://knowledge.digicert.com/generalinformation/INFO2824.html

See also

• Certificate: .pem, .ppk, .pfx, .p12, .cer, .crt, openssl pkcs12, .csr, .pub, PFX, PKCS, PKCS
• PEM, ssh-keygen -m PEM, RFC 1421, OpenSSH PEM (RFC 4716)
• Certificate, CSR (PKCS10), /etc/letsencrypt/csr/, openssl req, X.509, [.pem, .cer, .csr], Kubernetes CertificateSigningRequest
• X.509, ASN.1, openssl x509, .pem, der, PFX, PKCS, SAN, openssl x509, CSR
• Certificate, certificate extensions (.pem, .pfx), CSR, .csr, root certificate, public certificate

https://serverfault.com/questions/9708/what-is-a-pem-file-and-how-does-it-differ-from-other-openssl-generated-key-file