Hi I was writing a program that imports private keys from a .pem file and create a private key object to use it later.. the problem I have faced is that some pem files header begin with
-----BEGIN PRIVATE KEY----- while others begin with
-----BEGIN RSA PRIVATE KEY----- through my search I knew that the first ones are PKCS#8 formatted but I couldn't know what format does the other one belongs to.
See https://polarssl.org/kb/cryptography/asn1-key-structures-in-der-and-pem (search the page for "BEGIN RSA PRIVATE KEY") (archive link for posterity, just in case).
BEGIN RSA PRIVATE KEY is PKCS#1 and is just an RSA key. It is essentially just the key object from PKCS#8, but without the version or algorithm identifier in front. BEGIN PRIVATE KEY is PKCS#8 and indicates that the key type is included in the key data itself. From the link:
The unencrypted PKCS#8 encoded data starts and ends with the tags:
-----BEGIN PRIVATE KEY----- BASE64 ENCODED DATA -----END PRIVATE KEY-----Within the base64 encoded data the following DER structure is present:
PrivateKeyInfo ::= SEQUENCE { version Version, algorithm AlgorithmIdentifier, PrivateKey BIT STRING } AlgorithmIdentifier ::= SEQUENCE { algorithm OBJECT IDENTIFIER, parameters ANY DEFINED BY algorithm OPTIONAL }So for an RSA private key, the OID is 1.2.840.113549.1.1.1 and there is a RSAPrivateKey as the PrivateKey key data bitstring.
As opposed to BEGIN RSA PRIVATE KEY, which always specifies an RSA key and therefore doesn't include a key type OID. BEGIN RSA PRIVATE KEY is PKCS#1:
RSA Private Key file (PKCS#1)
The RSA private key PEM file is specific for RSA keys.
It starts and ends with the tags:
-----BEGIN RSA PRIVATE KEY----- BASE64 ENCODED DATA -----END RSA PRIVATE KEY-----Within the base64 encoded data the following DER structure is present:
RSAPrivateKey ::= SEQUENCE { version Version, modulus INTEGER, -- n publicExponent INTEGER, -- e privateExponent INTEGER, -- d prime1 INTEGER, -- p prime2 INTEGER, -- q exponent1 INTEGER, -- d mod (p1) exponent2 INTEGER, -- d mod (q-1) coefficient INTEGER, -- (inverse of q) mod p otherPrimeInfos OtherPrimeInfos OPTIONAL }
Have a look at this. It gives possible BEGIN markers.
Copying the content from the above link for quick reference:
#define PEM_STRING_X509_OLD "X509 CERTIFICATE" #define PEM_STRING_X509 "CERTIFICATE" #define PEM_STRING_X509_PAIR "CERTIFICATE PAIR" #define PEM_STRING_X509_TRUSTED "TRUSTED CERTIFICATE" #define PEM_STRING_X509_REQ_OLD "NEW CERTIFICATE REQUEST" #define PEM_STRING_X509_REQ "CERTIFICATE REQUEST" #define PEM_STRING_X509_CRL "X509 CRL" #define PEM_STRING_EVP_PKEY "ANY PRIVATE KEY" #define PEM_STRING_PUBLIC "PUBLIC KEY" #define PEM_STRING_RSA "RSA PRIVATE KEY" #define PEM_STRING_RSA_PUBLIC "RSA PUBLIC KEY" #define PEM_STRING_DSA "DSA PRIVATE KEY" #define PEM_STRING_DSA_PUBLIC "DSA PUBLIC KEY" #define PEM_STRING_PKCS7 "PKCS7" #define PEM_STRING_PKCS7_SIGNED "PKCS #7 SIGNED DATA" #define PEM_STRING_PKCS8 "ENCRYPTED PRIVATE KEY" #define PEM_STRING_PKCS8INF "PRIVATE KEY" #define PEM_STRING_DHPARAMS "DH PARAMETERS" #define PEM_STRING_DHXPARAMS "X9.42 DH PARAMETERS" #define PEM_STRING_SSL_SESSION "SSL SESSION PARAMETERS" #define PEM_STRING_DSAPARAMS "DSA PARAMETERS" #define PEM_STRING_ECDSA_PUBLIC "ECDSA PUBLIC KEY" #define PEM_STRING_ECPARAMETERS "EC PARAMETERS" #define PEM_STRING_ECPRIVATEKEY "EC PRIVATE KEY" #define PEM_STRING_PARAMETERS "PARAMETERS" #define PEM_STRING_CMS "CMS"