lpc-rsa, a key extractor for RSA

RSA key extractor. More...

RSA key extractor.

To use the Public key cryptography routines in the crypto library, you need RSA keys. The ssh-keygen program can generate you an RSA key pair, or you may have received a public key generated by a third party. However, the RSA routines in the crypto library can not work with SSH format keyfiles, they have to be transformed into a different format first. This program does just that.
It reads an SSH format RSA keyfile from the standard input and generates a C file that contains the keys as constant data, in the format that the RSA routines in the library can use. That C file is printed on the standard output. If there's an error the program prints an error message on the standard error.
If you start the program without any command line switches, it will print a usage message and exit.

Usage

First you need an RSA key. The program can process RSA keys generated by the SSH package's ssh-keygen program. If you want to generate your own key (that is, your own private key/public key pair), then you have to run the ssh-keygen program:

ssh-keygen -b key_length -t rsa -f key_file

The key_length is the length of the key, in bits. The minimum is 768. The value 1024 is common but 2048 bit long keys are getting popular. The key_file argument is the name of the file where you want your key to be stored. Two files are generated by the program, key_file and key_file.pub of which the former contains your private key and the latter contains the public key. (Note that the private key file actually contains both the private and the public keys) These files look something like this:

key_file:

key_file.pub:

ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAIEAwYEbbdP/F8fkMrIGSCQyoXpvGSHT
Ji1FzrbETV9EKRIluN7r53RcWSdHyCG16PWpGYcCnfDojbjn9thcjQU8m+LCLE4B
U57RyGuUDGtr3oI4xLxTwBedM2eU9iPt86bM/yPYT7TmxkMHwNMpc4kh3POpUzgh
CQsTGzgkSDmuyks= user@hostname

When you want to transform a keyfile into a format usable by the RSA functions of the crypto library, you have to invoke the lpc-rsa program, the one of which the documentation you're now reading:

lpc-rsa options < key_file > mykeys.c

That is, the program reads a keyfile generated by ssh-keygen on the standard input and generates a C file on the standard output. The C file will contain the RSA key(s) in a format that's usable by the RSA functions in the library.

Options

-private -public -both One and only one of the above three options must be given. It makes the program to extract the public key, the private key or both keys, respectively. If, and only if you specified -public, then the program accepts a public key file on the input (but it still accepts the private key file as well). For the other two cases you must pass the private key file to the program. Using the public key file might be necessary if the keys are generated by a third party, in which case naturally you only have access the public key.

-stem identifier
The extracted key(s) are stored in structures. This option sets the name stem for the structures. The default is rsa. The structure(s) defined in the C file will be

const BC_RSA_PUBLIC_KEY stem_public_key; const BC_RSA_PRIVATE_KEY stem_private_key;

for the public and/or private key, respectively.

Exit code

0 : success
1 : command line error
2 : key file error

lpc-rsa, a key extractor for RSA [LPC2xxx related tools running on the host]

Usage

Options

Exit code

lpc-rsa, a key extractor for RSA
[LPC2xxx related tools running on the host]