# What is the format of RSA Public Key?

## What is the format of RSA Public Key?

An RSA public key consists of two values: n A long integer called the RSA modulus. e A positive integer, often small, called the RSA public exponent.

### How are RSA keys calculated?

The keys for the RSA algorithm are generated in the following way:

- Choose two distinct prime numbers p and q.
- Compute n = pq.
- Compute λ(n), where λ is Carmichael’s totient function.
- Choose an integer e such that 1 < e < λ(n) and gcd(e, λ(n)) = 1; that is, e and λ(n) are coprime.

**How many bits should an RSA key be?**

For RSA keys, the minimum size for clear RSA keys and secure RSA keys on the public key data set (PKDS) is 512 bits. The minimum size for secure RSA keys on the token key data set (TKDS) is 1024 bits and the size must be a multiple of 256.

**What is 2048 bit RSA key?**

Measuring encryption strength NIST tells us a 2048 bit RSA key is equivalent to a 112 bit symmetric cipher. NIST says a 2048 bit RSA key has a strength of 112 bits: i.e., there are theoretically 2112 possibilities to crack the private key.

## Can a RSA key be converted to a PEM key?

In OpenSSL v1.0.1 genrsa is superseded by genpkey so this is the new way to do it ( man genpkey ): If you have an RSA key pair in DER format, you may want to convert it to PEM to allow the format conversion below:

### What is the format for the SSH RSA key?

The “ssh-rsa” key format has the following specific encoding: string “ssh-rsa” mpint e mpint n For example, at the beginning, you get 00 00 00 07 73 73 68 2d 72 73 61. The first four bytes (00 00 00 07) give you the length.

**How to calculate the length of a RSA key?**

For example, at the beginning, you get 00 00 00 07 73 73 68 2d 72 73 61. The first four bytes ( 00 00 00 07) give you the length. The rest is the string itself: 73=s, 68=h, -> 73 73 68 2d 72 73 61 = ssh-rsa, followed by the exponent of length 1 ( 00 00 00 01 25) and the modulus of length 256 ( 00 00 01 00 7f ).

**Which is the OID of the RSA public key?**

So for an RSA public key, the OID is 1.2.840.113549.1.1.1 and there is a RSAPublicKey as the PublicKey key data bitstring. The RSA private key PEM file is specific for RSA keys. It starts and ends with the tags: Within the base64 encoded data the following DER structure is present: