# autoroll.key

#### micromouse

##### Inactive User
Hi,

Can some gurus explain the meaning of E1, N1, N2, N2a in the autoroll.key???? i know we can not suppose to touch that but i really want to know where the value can be found. I did a compare of the key in autoroll.key with the image of mosc. N2 is the emm decryt n V is the verify key. What is E1, N1, N2a and where can we find this value?

Cheers

#### micromouse

##### Inactive User
hi,

i searched n read and found this from 1 of the post by nozzer.

Parity keys themselves are a very special compressed form of the RSA P and Q keys from which further RSA keys E (Exponent) and N (Modulus) can be derived.

The Nagra Emm algorithm is actually a double RSA encryption -

E(M) = (M^3 mod N1) ^ E2 mod N2
D(M) = (M^3 mod N2) ^ E1 mod N1

Where -

E(M) is the definition of the encryption function
D(M) is the definition of the decryption function
M is your 64 byte Emm string (plaintext if encrypting)
N1 is the first modulus (derived from ParityKey - N1 = P * Q )
E1 is the first exponent (derived from ParityKey - E1 = (2(P-1)(Q-1)+1)/3 )
N2 is the 2nd modulus (64 byte Emm decrypt key from Tier7 on card)
E2 is the 2nd exponent. This value is known only to the cc's !

Can some1 advise where to find the P and Q in the card image. Trying to fix a autoupdate for my CC.

Cheers

#### micromouse

##### Inactive User
after more reading, i used the emmstudio to generate the n1 ans e1 but wouldnt au. i have pk 0, 1 and 2, which 1 shld i used?

Cheers

TEST