Hello there, I'm trying to figure out how MS-MPPE-Send-Key and MS-MPPE-Recv-Key are getting generated by freeradius-server. Here, it is the sample captured traffic I've for a MS-CHAPv2 (Access-Accept) auth between a radius client and server: MS-MPPE-Recv-Key: a660ce53f31ef08ed6cf209ece137a1dee40aeae5d8e5b9de0f1592324bc92569fc1 MS-MPPE-Send-Key: a81579eb58f0bd25636599778c8689516129db8b25ec2d1e4c15797862efedabb3c So, the first thing I noticed here is that the length of the values for both AVPs are 34 bytes. I read rfc2548 and rfc3079 for this matter and then tried to find corresponding implementations in the code-base (src/modules/rlm_mschap/rlm_mschap.c), and found "mppe_chap2_gen_keys128" function. The function is being called by "mod_authenticate_resume" : /* now create MPPE attributes */ if (inst->use_mppe) { fr_pair_t *vp; uint8_t mppe_sendkey[34]; uint8_t mppe_recvkey[34]; switch (mschap_version) { case 1: RDEBUG2("Generating MS-CHAPv1 MPPE keys"); memset(mppe_sendkey, 0, 32); /* * According to RFC 2548 we * should send NT hash. But in * practice it doesn't work. * Instead, we should send nthashhash * * This is an error in RFC 2548. */ /* * do_mschap cares to zero nthashhash if NT hash * is not available. */ memcpy(mppe_sendkey + 8, nthashhash, NT_DIGEST_LENGTH); mppe_add_reply(inst, request, tmpl_attr_tail_da(env_data->chap_mppe_keys), mppe_sendkey, 24); //-V666 break; case 2: RDEBUG2("Generating MS-CHAPv2 MPPE keys"); mppe_chap2_gen_keys128(nthashhash, response->vp_octets + 26, mppe_sendkey, mppe_recvkey); mppe_add_reply(inst, request, tmpl_attr_tail_da(env_data->mppe_recv_key), mppe_recvkey, 16); mppe_add_reply(inst, request, tmpl_attr_tail_da(env_data->mppe_send_key), mppe_sendkey, 16); break; default: fr_assert(0); break; } MEM(pair_update_reply(&vp, tmpl_attr_tail_da(env_data->mppe_encryption_policy)) >= 0); vp->vp_uint32 = inst->require_encryption ? 2 : 1; MEM(pair_update_reply(&vp, tmpl_attr_tail_da(env_data->mppe_encryption_types)) >= 0); vp->vp_uint32 = inst->require_strong ? 4 : 6; } /* else we weren't asked to use MPPE */ Correct me if I'm wrong but here I read " mppe_sendkey" and " mppe_recvkey" variables are initialized with 34 bytes (as i expected!), but later by calling mppe_chap2_gen_keys128 only 16 bytes are copied. I was expecting other items (such as 'Salt') to be taken into account too .. Thanks.