DER vs. CRT vs. CER vs. PEM Certificates and How To Convert Them
Quote from the support page:
View
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Even though PEM encoded certificates are ASCII they are not human
readable. Here are some commands that will let you output the
contents of a certificate in human readable form;
View PEM encoded certificate
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Use the command that has the extension of your certificate replacing
cert.xxx with the name of your certificate
openssl x509 -in cert.pem -text -noout
openssl x509 -in cert.cer -text -noout
openssl x509 -in cert.crt -text -noout
If you get the folowing error it means that you are trying to view a DER encoded certifciate and need to use the commands in the “View DER encoded certificate
below”
unable to load certificate
12626:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:647:Expecting: TRUSTED CERTIFICATE View DER encoded Certificate
View DER encoded Certificate
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openssl x509 -in certificate.der -inform der -text -noout
If you get the following error it means that you are trying to view a PEM encoded certificate with a command meant for DER encoded certs. Use a command in the “View PEM encoded certificate above
unable to load certificate
13978:error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1306:
13978:error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error:tasn_dec.c:380:Type=X509