1. Cracking Net2Phone and other VoIP technologies by Todd Moore

2. Cracking Net2Phone Net2Phone and many other VoIP technologies are not safe from wiretaps Dialed phone numbers easily decrypted Conversations can be reconstructed for playback

3. Net2Phone Dialed Numbers 00000036 : 5E 6E 65 77 63 61 6C 6C 34 5F 65 6D 20 31 39 32 [^newcall4_em 192] 00000046 : 2E 31 36 38 2E 30 2E 31 30 31 20 36 38 30 31 20 [.168.0.101 6801 ] 00000056 : 36 38 30 31 20 34 36 32 35 32 31 36 36 33 30 20 [6801 4625216630 ] 00000066 : 34 36 32 35 32 31 36 36 33 30 20 38 30 31 35 37 [4625216630 80157] <-1 00000076 : 46 39 30 44 42 31 46 32 44 39 30 20 38 30 31 35 [F90DB1F2D90 8015] <-2 00000086 : 37 46 39 30 38 31 31 46 37 45 39 39 38 31 31 34 [7F90811F7E998114] 00000096 : 37 45 39 31 38 31 31 34 33 44 39 31 20 63 65 33 [7E9181143D91 ce3] 000000a6 : 2E 30 2F 34 35 20 53 36 39 34 32 35 35 37 31 31 [.0/45 S694255711] 000000b6 : 38 34 38 35 35 37 39 31 42 34 37 35 35 37 33 33 [84855791B4755733] 000000c6 : 37 33 34 31 46 37 35 20 32 33 37 33 20 38 30 31 [7341F75 2373 801] 000000d6 : 35 37 46 39 30 44 45 31 46 37 44 39 33 44 46 35 [57F90DE1F7D93DF5] 000000e6 : 37 32 32 44 30 20 4E 50 43 44 30 31 52 32 31 30 [722D0 NPCD01R210] 000000f6 : 20 65 6E 20 4E 32 50 20 30 20 66 72 6F 6D 5C 33 [ en N2P 0 from\3] 00000106 : 44 62 65 68 65 61 64 65 72 32 5C 32 30 61 6C 74 [Dbeheader2\20alt] 00000116 : 63 6F 64 65 63 5C 33 44 35 30 2C 36 30 2C 32 30 [codec\3D50,60,20] 00000126 : 2C 33 30 2C 31 30 5C 32 30 70 69 6E 5C 33 44 66 [,30,10\20pin\3Df] 00000136 : 61 6C 73 65 20 0A [alse.] 1=key 2=encoded phone number Captured packet containing phone number

4. Net2Phone Algorithm Key: k1k2k3k4 Code: c1c2c3c4 c1c2c3c4 c1c2c3c4 … Decode: k1k2k3k4 xor c1c2c3c4 = r1r2r3r4 Order: r4r2r1r3 Dialed: 1 (123) 456-7890 Key: 33BB6E01 Code: 33BB6F01 = 00000100 = 00000001 32B16C01 = 010A0200 = 000A0102 36BF6802 = 05040603 = 03040506 3AB36E06 = 09080007 = 07080900

5. Conversation Playback RTP is commonly used protocol for Voice- over-IP (VoIP) communications struct RTP_Header { // byte 1: unsigned char csrc_count:4; unsigned char extension :1; unsigned char padding :1; unsigned char version :2; // byte 2 unsigned char payload_type:7; unsigned char marker:1; // byte 3-4 unsigned short seq_num; // byte 5-8 unsigned int timestamp; // byte 9-12 unsigned int ssrc; } rtp

6. Conversation Playback Most important fields are Payload_Type and Timestamp Payload type will tell you the type of audio codec to use (0=ULAW, 2=ADPCM, 4=G.723, 8=G.711 ALAW, etc) Timestamp will tell you when the audio should be played and if there are silence gaps (silence is not transmitted)

7. Conversation Playback 5 Steps for audio replay from capture 1.Reassemble 2.Decompress 3.Fill Silence Gaps 4.Adjust Starting Time 5.Mix & Play

8. Conversation Playback 1. Reassemble - Reassemble RTP packets into two streams ip1:port1 to ip2:port2 and ip2:port2 to ip1:port1 Stream 1 Stream 2 192.168.1.112 : 49604 -> 192.168.1.83 : 49604 192.168.1.83 : 49604 -> 192.168.1.112 : 49604 rtp

9. Conversation Playback 2. Decompress - Determine the audio codec used and uncompress payload of each packet RTP PT=4 uncompressed G.723 compressed CODEC Decompression

10. Conversation Playback 3. Fill Silence Gaps - Determine the minimum timestamp interval for each individual stream and fill in any silence gaps rtp Time: +600 +900 +300 +300 (min: 300) 1 gap 2 gaps rtp Time: +300 +300 +300 +300 +300 +300 +300 rtp Insert silence for each gap

11. Conversation Playback 4. Adjust Starting Time - Add silence gap to the late starting stream based on packet capture time Stream 1 Stream 2 rtp +2 seconds +300 +300 +300 Stream 2 rtp First packet of this stream was captured +2 seconds after the other stream Fill in silence gap so the two streams are in sync Stream 1 rtp +300 +300 +300

12. Conversation Playback 5. Mix & Play - Mix both uncompressed streams for audio playback Stream 2 Stream 1 Mix

13. Demo of VoIP Replay Demo of VoIP replay using NetWitness® Reader NetWitness® Reader with demo data available for download at www.NetWitness.comwww.NetWitness.com