ssh: id_rsa não funciona, mas se eu renomeá-lo, ele funciona

Eu tenho esse id_rsa na minha pasta ~ / .ssh. Mas isso simplesmente não se autentica. Se eu copiá-lo e renomeá-lo para algo que não seja id_rsa, ele funciona.

[qfan@mycomputer .ssh]$ ls -al id_rsa id_rsa_good
-rw------- 1 qfan qfan 1766 Dec  3 18:35 id_rsa
-rw------- 1 qfan qfan 1766 Nov 20 19:43 id_rsa_good
[qfan@mycomputer .ssh]$ sha1sum id_rsa id_rsa_good
8cc7f68170038b184bba0541be7d105bb36f7d11  id_rsa
8cc7f68170038b184bba0541be7d105bb36f7d11  id_rsa_good
[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa
qfan@localhost's password: 

[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa_good
Enter passphrase for key 'id_rsa_good': 
Last login: Tue Dec  3 18:46:46 2013 from 127.0.0.1
[qfan@mycomputer ~]$ exit
logout
Connection to localhost closed.

Observe que "ssh localhost -i id_rsa" falha e o ssh começa a solicitar o login regular da senha.

Eu usei -vvv e aqui está o diff dos logs:

[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa_good -vvv 2> log1_good.txt
Enter passphrase for key 'id_rsa_good': 

[qfan@mycomputer .ssh]$ ssh localhost -i id_rsa -vvv 2> log2_bad.txt
qfan@localhost's password: 

[qfan@mycomputer .ssh]$ diff log1_good.txt log2_bad.txt 
7c7
< debug3: Not a RSA1 key file id_rsa_good.
---
> debug3: Not a RSA1 key file id_rsa.
41c41
< debug1: identity file id_rsa_good type -1
---
> debug1: identity file id_rsa type 1
81,82c81,82
< debug2: dh_gen_key: priv key bits set: 126/256
< debug2: bits set: 533/1024
---
> debug2: dh_gen_key: priv key bits set: 127/256
> debug2: bits set: 503/1024
90c90
< debug2: bits set: 506/1024
---
> debug2: bits set: 539/1024
103c103
< debug2: key: id_rsa_good ((nil))
---
> debug2: key: id_rsa (0x7f953ea96f90)
136,138c136,145
< debug1: Trying private key: id_rsa_good
< debug1: PEM_read_PrivateKey failed
< debug1: read PEM private key done: type <unknown>
---
> debug1: Offering public key: id_rsa
> debug3: send_pubkey_test
> debug2: we sent a publickey packet, wait for reply
> debug3: Wrote 368 bytes for a total of 1477
> debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
> debug2: we did not send a packet, disable method
> debug3: authmethod_lookup password
> debug3: remaining preferred: ,password
> debug3: authmethod_is_enabled password
> debug1: Next authentication method: password
[qfan@mycomputer .ssh]$ 

Também tentei remover a senha do arquivo de chave, mas ainda não funcionará se nomeada id_rsa.

Então, o que deu errado lá?

-------EDITAR-------

[qfan@mycomputer .ssh]$ file id_rsa
id_rsa: ASCII text
[qfan@mycomputer .ssh]$ cat id_rsa |head -n2
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED

Encontrei o motivo. Meu id_rsa.pubarquivo na mesma .sshpasta é uma chave pública que pertence a um arquivo de identidade diferente. Quando id_rsa.pubnão corresponde id_rsa,, falha automaticamente. Remover ou mover o id_rsa.pubarquivo dá id_rsacerto.