Question: I`m trying to convert the .cer file to .pem through openssl, the command is:

```
openssl x509 -inform der -in certnew.cer -out ymcert.pem

```

and that's the errors I`m getting:

```
unable to load certificate
140735105180124:error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag:tasn_dec.c:1319:
140735105180124:error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error:tasn_dec.c:381:Type=X509

```

What am I doing wrong?

Answer: 
I had this problem also. Just rename the CER to PEM was enough :)
I have similar issue with CRT format which give me error during converting to pem. I do same thing like L0g0ff and it works. Below more details.

1. I checked details of certificate: 

`openssl x509 -in certificate.crt -noout -text`
2. after changing extension to from certificate.crt to certificate.pem I get file in expected format:

`-----BEGIN CERTIFICATE-----
...........................
-----END CERTIFICATE-----`