Signing data bigger than allowed RSA Block size?
Dont hate me if a similar question has already been posted (yes, i've been looking around)

Anyways, i've enountered a small problem while implementing a modified version of the 
*Station-To-Station* protocol (STS). For the second protocol message, i want to encrypt (using my private key) some data using public key encryption (e.g. RSA); and as STS is a keyagreement protocol used for establishing a secret key, symmetric encryption such as AES or 3DES cannot be used. 

Furthermore, i thought of just hashing the data to some fixed size (using e.g. SHA-1) and then signing it; however that will not work either, since the other partie must be able to extract the different parts of the signed message for some later verification check.

In case i was unclear: **SigB(Tb,Ta,A)** where **SigB** means signing using private key B; *Ta,Tb and A* are data that i must be able to retrive.

Is there some other way besides chopping up the data into blocks and then signing each such block (ECB, which is vulnerable to crypto analysis)?

Best Regards,

jonas



Signing data bigger than allowed RSA Block size?
===

Dont hate me if a similar question has already been posted (yes, i've been looking around)

Anyways, i've enountered a small problem while implementing a modified version of the 
*Station-To-Station* protocol (STS). For the second protocol message, i want to encrypt (using my private key) some data using public key encryption (e.g. RSA); and as STS is a keyagreement protocol used for establishing a secret key, symmetric encryption such as AES or 3DES cannot be used. 

Furthermore, i thought of just hashing the data to some fixed size (using e.g. SHA-1) and then signing it; however that will not work either, since the other partie must be able to extract the different parts of the signed message for some later verification check.

In case i was unclear: **SigB(Tb,Ta,A)** where **SigB** means signing using private key B; *Ta,Tb and A* are data that i must be able to retrive.

Is there some other way besides chopping up the data into blocks and then signing each such block (ECB, which is vulnerable to crypto analysis)?

Best Regards,

jonas


