How could a temporary RSA key be verified when it was signed with a public key affected by crypto export restrictions?

I think it's about right.In a nutshell, the regulations were only used as ciphers and signatures were fine.

A1.FREAK attacks use SSL protocol vulnerabilities and unqualified client implementations.Only a strong key is signed to the Certificate Authority, providing a temporarily created weak key if a client under export restrictions requires a weaker key (rewritten to request a weak key from the middleman in a FREAK attack).

A2. The weak key is signed with a strong private key signed by the certificate authority.This signature can be verified with a strong public key.

A3. Export restrictions are only used as encryption of high-bit RSA and do not include signatures, so you could sign them with bits of the size that would otherwise be restricted ( source is linked 22(d) Cryptographic Algorithms).

As for why regulations are only used for cryptography, I couldn't find anything written on it, so it's my idea from here on out, so the reason may be wrong.
In RSA, public and private keys are mathematically reversed, such as addition and subtraction.So when you create a key pair, you can use either of the keys as a public key, and if you use both keys in any order, the output will be the same as the input.
This is what we apply to be able to encrypt and sign in one pair.

• When encrypting, encrypt with a public key and decrypt with a private key (only people with private keys can read).
• Use a private key when signing and a public key for verification (only people with private keys can sign).

Now, if you compare the processing of a signature to the processing of a cipher, the confirmation of the signature is the decryption of the cipher.There is no reason to be regulated because the data is published (RSA's algorithm is published in a paper, so anyone who can write programs could write software that uses high bits).