Foundations of Network and Computer Security John Black

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Foundations of Network and Computer Security John Black Lecture #17 Oct 9, 2009 CSCI 6268/TLEN 5550, Fall 2009

CSR: Certificate Request • You will generate a CSR – Certificate Request • Has your name, email, other info, your public key, and you sign it • Send your CSR to the CA – CA will sign it if it is properly formatted – His signature overwrites your signature on the CSR • Once CA signs your CSR it becomes a certificate

Creating a CSR % openssl req -key john-priv. pem -new -out john-req. pem Enter pass phrase for john-priv. pem: You are about to be asked to enter information that will be incorporated into your certificate request. Country Name (2 letter code) [AU]: US State or Province Name (full name) [Some-State]: Colorado Locality Name (eg, city) []: Boulder Organization Name (eg, company) [Internet Widgits Pty Ltd]: University of Colorado Organizational Unit Name (eg, section) []: Computer Science Common Name (eg, YOUR name) []: John Black Email Address []: jrblack@cs. colorado. edu (Leave the rest blank) This outputs the file john-req. pem which is a cert request

Viewing a CSR % openssl req -in john-req. pem -text -noout Note: not password protected Certificate Request: Data: Version: 0 (0 x 0) Subject: C=US, ST=Colorado, L=Boulder, O=University of Colorado, OU=Computer Science, CN=John Black/email. Address=jrblack@cs. colorado. edu Subject Public Key Info: Public Key Algorithm: rsa. Encryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00: ca: 40: b 9: ef: 31: c 2: 84: 73: ab: ef: e 2: 6 d: 07: 17: 83: 5 e: 96: 46: 24: 25: 38: ed: 7 a: 60: 54: 58: e 6: f 4: 7 b: . . . 27: de: 00: 09: 40: 0 c: 5 e: 80: 17 Exponent: 65537 (0 x 10001) Attributes: a 0: 00 Signature Algorithm: md 5 With. RSAEncryption 32: e 1: 3 f: e 2: 12: 47: 74: 88: a 3: f 9: f 4: 44: 8 a: f 3: b 7: 4 e: d 1: 14: 1 f: 0 b: be: b 8: 19: be: 45: 40: ed: 5 b: fb: ab: 9 b: 01: e 8: 9 a: 26: 0 c: . . . 9 c: e 0 CSR is signed by you

CSRs • Why is your CSR signed by you? – Ensures that the CSR author (you) have the private key corresponding to the public key in the CSR • If we didn’t do this, I could get the CA to sign anyone’s public key as my own – Not that big a deal since I can’t decrypt things without the corresponding private key, but still we disallow this • Why does the CA sign your public key – Well, because that’s his reason for existence, as discussed previously – Ok, let’s say I email my CSR to the CA and he signs it… then what?

Sample Certificate -----BEGIN CERTIFICATE----MIIDk. DCCAnig. Aw. IBAg. IBCz. ANBgkqhki. G 9 w 0 BAQQFADCBg. TEQMA 4 GA 1 UEAx. MHSm 9 o bi. BDQTERMA 8 GA 1 UECBMIQ 29 sb 3 Jh. ZG 8 x. Cz. AJBg. NVBAYTAl. VTMSYw. JAYJKo. ZIhvc. N AQk. BFhdqcm. Js. YWNr. QGNz. Lm. Nvb. G 9 y. YWRv. Lm. Vkd. TEl. MCMGA 1 UECh. Mc. Um 9 vd. CBDZXJ 0 a. WZp. Y 2 F 0 a. W 9 u. IEF 1 d. Ghvcml 0 e. TAe. Fw 0 w. Mz. Ex. MTMy. MDQ 1 Mj. Fa. Fw 0 w. NDEx. MTIy. MDQ 1 Mj. Fa. MIGFMRIw. EAYDVQQDEwl. UZXN 0 IFVz. ZXIx. ETAPBg. NVBAg. TCENvb. G 9 y. YWRv. MQsw CQYDVQQGEw. JVUz. Ej. MCEGCSq. GSIb 3 DQEJARYUd. GVzd. EBjcy 5 jb 2 xvcm. Fkby 5 l. ZHUx Fj. AUBg. NVBAo. TDVVua. XYg. Q 29 sb 3 Jh. ZG 8 x. Ej. AQBg. NVBAs. TCUNTQ 0 kg. NDgz. MDCCASIw DQYJKo. ZIhvc. NAQEBBQADgg. EPADCCAQo. Cgg. EBAL 1 k 6 h. J 9 gw. Xl. UYHi. FOm 6 OHOf+8 Y 0 o 1 b 7 WOex. Yf. NDWm 9 H 0 I 79 o 0 w. Vg. Dj 7 wa. Ogt 4 hz 2 FE 2 h+g. Arf. GY 5 Vsa. Szm. CH 0 EA 4 k. DS m/s. Pob 3 HTVpb. IFwlb. XTV 7 h. C 0 Ox. Oz. Rs 8 lph. Ddj 1 va. NDSn. Owq. OS 1 ADCf. Ida. GEh 9 WKi r. Ed. Fdriiu 7 v 1 bw+c 1 By. M 57 v 9 a. HO 7 Rslsw. R 9 En. RFZPWYa 8 Gp. K+St 0 s 8 b. ZVf 98 IOOk H 8 Hiliy. VSt 5 l. AXRMn. Ixh. YMG 89 tkku. CAwxg. DD+7 Wqy. ETYx. Y 0 UCg/jo. FV 4 IKc. C 7 W 1 b Cmvxs. Y 6/H 35 Up. Ggv 0 an. Ckjy. P 0 m. KY/YWB 9 KXwr. R 8 NHC 7/hacij 0 YNi. V 77 EIMCAw. EA Aa. MNMAsw. CQYDVR 0 TBAIw. ADANBgkqhki. G 9 w 0 BAQQFAAOCAQEAZr 4 hd. QPc. Gn. AYmk++ 0 b. Q 4 UKILXj 9 wr 7 UZdgz 3 DKJNp. MPk. Fjz. U 6 wv. Jrd 1 C 8 KIKf. JC 63 TKHJ 7 svmd. Zw. TCB 2 h. NUFy 8 kbe 2 Kv. NWQi. Go. X 3 Pa. Y 1 eo 3 au. Lz. Ii 8 Ix. Pq. N+W/p 1 z 3 Mhtp. Qq. Nllqz. G 8 G 1 o 50 QP 2 y. Ayj 2 V 0 rnwl. RL 3 k. Z 7 ibv. XRn. SB 1 Bz+6 z. JJLAQr 4 k. TQD 2 Efx. Lhpks+i. SE+m 58 PV tfck 25 o 2 IMJYYLAdto. NGjc. FG 9/a. Dk+GHbsx 8 LP/va 6 B 6 BIz. B 3 vrefu. Qv. Bu+7 j/mz a. XP 7 Qku. GYf 1 r 4 yy. Oiu. MYnw 0 kwp 5 xnd. DKTz. ORsxks. HQk 5 AWf. BXr. Dd. GPZrb 6 i 1 Ul. Oq U/P 3+A== -----END CERTIFICATE----- Ooh…how useful!

Viewing a Certificate % openssl x 509 -in john-cert. pem -text –noout Certificate: Again, no encryption Data: Version: 3 (0 x 2) Serial Number: 1 (0 x 1) Signature Algorithm: sha 1 With. RSAEncryption Issuer: CN=Martin Cochran, ST=Colorado, C=US/ email. Address=Martin. Cochran @colorado. edu, O=University of Colorado Validity Not Before: Oct 7 19: 52: 43 2007 GMT Not After : Oct 7 19: 52: 43 2008 GMT Subject: C=US, ST=Colorado, L=Boulder, O=University of Colorado, OU=Computer Science, CN=John Black/email. Address=jrblack@cs. colorado. edu Subject Public Key Info: Public Key Algorithm: rsa. Encryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00: ca: 40: b 9: ef: 31: c 2: 84: 73: ab: ef: e 2: 6 d: 07: 17: 83: 5 e: 96: 46: 24: 25: 38: ed: 7 a: 60: 54: 58: e 6: f 4: 7 b: . . . 27: de: 00: 09: 40: 0 c: 5 e: 80: 17 Exponent: 65537 (0 x 10001) Signature Algorithm: sha 1 With. RSAEncryption 97: 4 a: 20: ea: a 7: 5 a: 4 d: 4 c: 77: b 9: 3 e: c 0: 49: 9 b: ab: 8 f: 6 f: 02: 53: 24: a 9: 71: 97: 2 c: 1 f: e 8: e 4: eb: d 0: f 6: 6 a: 7 c: 74: 30: 1 d: 9 e: . . . 3 a: 59 Now it’s the CA’s signature

What have we Accomplished? • We have an X. 509 cert – It contains our public key, name, email, and other stuff – It is signed by the CA • You have a private key in a password-protected file – Don’t lose this file or forget the password! • What else do we need? – We need to be able to verify the CA’s signature on a public key! – We therefore need the CA’s verification key

CA’s Verification Key is a Cert! • The CA generates a self-signed “root certificate” – This is his verification key (aka public key) which he signs – This certificate is what is embedded in your browser – This certificate is used to validate public keys sent from other sources – My root certificate will be used to validate all public keys for our class

My Root Cert -----BEGIN CERTIFICATE----MIICkj. CCAfug. Aw. IBAg. IJAJk. QJeqat 8 EHMA 0 GCSq. GSIb 3 DQEBBAUAMIGBMRAw. Dg. YD VQQDEwd. Kb 2 hu. IENBMREw. Dw. YDVQQIEwh. Db 2 xvcm. Fkbz. ELMAk. GA 1 UEBh. MCVVMx. Jj. Ak Bgkqhki. G 9 w 0 BCQEWF 2 py. Ymxh. Y 2 t. AY 3 Mu. Y 29 sb 3 Jh. ZG 8 u. ZWR 1 MSUw. Iw. YDVQQKExx. S b 290 IENlcn. Rp. Zmlj. YXRpb 24 g. QXV 0 a. G 9 ya. XR 5 MB 4 XDTA 5 MTAw. NTE 3 NTg 1 M 1 o. XDTEw MTAw. NTE 3 NTg 1 M 1 owg. YEx. EDAOBg. NVBAMTB 0 pva. G 4 g. Q 0 Ex. ETAPBg. NVBAg. TCENvb. G 9 y YWRv. MQsw. CQYDVQQGEw. JVUz. Em. MCQGCSq. GSIb 3 DQEJARYXan. Jib. GFja 0 Bjcy 5 jb 2 xv cm. Fkby 5 l. ZHUx. JTAj. Bg. NVBAo. THFJvb 3 Qg. Q 2 Vyd. Glma. WNhd. Glvbi. BBd. XRob 3 Jpd. Hkw g. Z 8 w. DQYJKo. ZIhvc. NAQEBBQADg. Y 0 AMIGJAo. GBAK 7 d. KVblnjz 73 FRZ+N 5 Vy 5 FVA 9 Q 4 q/k. Aoy. WWo. Rz. I 8 a. N 97 HUu. Ov. CPu. Xo. Mevl. TJkkpm. DXXF 2 fycy. DGY 2 qz. NWS 7 PTG 0 qk. CG ZF/5 ULH 3 Pn. JJau 2 KPcd. XIa. Q 6 r 0 Sqwz. Cb. VS 4 K 6 RGGk 52 b. Raxvf. Pe. Brh. Dhhlge. Zz. PG IRPCq. IV 43 DHGw. FYh. Ag. MBAAGj. EDAOMAw. GA 1 Ud. Ew. QFMAMBAf 8 w. DQYJKo. ZIhvc. NAQEE BQADg. YEAp. F 8 fqdzv 5 w 9 Lu. Iehc. B+m 8 C/d. Ebp. GOSm+sg. Th. Ds. Rp. WGele. Xs/szs 29 G 1 V 48 KG 9 ux. CRz 2 j. Tkj 8 pe. PUdp 8 Cs. G 5 yw. Udigx 1 qk. TRl+Vjy 7 q. PPl. Pv. GRHbql/fi/o. AH Rtst. VRjmjq. KIG 3 h. EZJHghow. CC+4 ibfw 2 jg. PVt. Cg. Lkh. R 713 u. Rim 8= -----END CERTIFICATE-----

How to Distribute the Root Cert? • It’s ridiculous for me to ask you to write this down, right? – If I email it to you, it might get altered by an adversary – If I put it on the web page, it might get altered by an adversary – Ok, this is probably not a REAL concern for us, but we’re practicing being paranoid – What can we do?

Distributing the Root Cert • Fingerprint the root certificate! – We’ll just distribute the fingerprint as a verification check – The cert itself will be distributed via some insecure means – The fingerprint will use a collision-resistant hash function, so it cannot be altered – But now we have to distribute the fingerprint • This you can write down, or I can hand you a hardcopy on a business card, etc • People used to have a fingerprint of their PGP public key on their business cards at conferences… haven’t seen this in a while though

Root Cert Fingerprint % openssl x 509 -in cacert. pem -fingerprint –noout SHA 1 Fingerprint= 4 E: 12: 84: 6 B: 85: 37: 78: E 8: 8 A: 7 B: DA: BA: 8 F: F 9: A 6: ED: 6 F: 44: 78: 68 • Please write this down now • And, yes, some is going to point out that perhaps my powerpoint was infiltrated during the night, so I’ll check against my hardcopy

Overall Idea of the Project • Each student has a cert containing a public key corresponding to his private key • Each student knows the verification key of the CA • Student A wants to send secure mail message M to student B – A obtains B’s cert and verifies it is correctly signed by the CA – A chooses a random session key K and RSA encrypts using B’s public key (from B’s cert) – A writes out the encrypted K followed by M encrypted symmetrically, then signs each of these with her private key and sends to B • B receives all of this and… – – Obtains A’s cert and verifies it is signed by CA B verifies A’s signature on the message B uses his private key to decrypt K (session key used by A) B uses K to decrypt M

Sample Message from A to B RSA Encrypted Session Key K -----BEGIN CSCI 6268 MESSAGE----hjh 2 vke. SGp. Weh. Awg. MOEb. Koms. W 3 l. Td 8 BBBr. Ef. Fchb. AZpnbc+O 7 wc. I 8 OT 0 g 9 WP 9 i. PV K 92 xbz. Ai. Vl. AN 7 ZFOWlx/i. X 2 XQIb. UQBU 6 kl 7 NOy. PTt. SZ/5+9 JHVDY 1 TFZG 3 c. Gt. Vj 5 Se. J 97+kvu. Wk. Zv. Nc. Kj. Aec 1 Yb. RYp. XRGw. Rmq. Ptz+o 5 WYWq. Wmq. PV 6 l. QWjb. N 4 Jc+w 2 Gcl FKR 7 t 0 Zsi 5 Rcn. Ew. In+c. Ztu. Te 3 QWW 4/in. MGMBFgb. Xj. A 2 E 6 VU 7 zn 62 Bd. BHh 7 S 1/o. BR tt 84 Rr 4/o. XXJhr. EASd. ZJEd. Gw 8 trh 0 FPd 48 io. HEl. T 7 TNGMx 4 YJKHBV 1+EMj. Tc. Hwd. N DCr 29 AZ 2 Qy. Dh/p. HYqv. Jm. Vg== AES-128 -CBC encrypted message M U 2 Fsd. GVk. X 1/QUjgfw 4 j. EV 34 P/Efn 8 Ub 7 NDz. V 5 QL+u. Woe. Dblsp. Qiz 2 Bi. Pq. QEa 1 acb CD 2+Xg. D 36 Fmmc. P 9 Wx. DOd. Q 63 Al. X 2 K 4 t 4 Sd. Sy. TT 8 uk 9 Ypd. UC 0 thq. CXFk. DGM 6 P 0 u 7 Xx g. Bx. P 0 s 0 mtc. NFKbcpwmi. Ep 5 K 8 ay. GHs. YW 5 l. M 2 ve. Fcl. VL 75 x. Re. QGA 8 fkj. Z 3 OQQe. R+nz n. QTg 2 Hniyaniwbb 11 Yg. Bmy. WQ 4 bs. VK 5 UDG 0 i. Yab 100 cv. PUl. FZXr. Mm. K 4 aum. MNt. C+0 Z +Syj 4 Fa. Pz. Uphhebhuhs. U 29 tahd 8 h. L 9 DZQ 5 Zuz. Zi 5 hy 0 n. G 5 z 45 FHktap/bww. OGC Iu 3 m. RM 6 Zqo. TVVan. Tqf 0 c. Ba. RA 5 c+XJbhu. XLxj. S 44 vi. FKSKENm. Z 7 p. EPZtdisvd/aq 2 we. Zb 1 am. Cy 2 jn. P 0 x. Qio. I 8 Lc/zkno 5 XRW 21 b. GH 3 k. We. G 8 k. Mu. Or. BKVyms 2 FOEps. I 0 TH 0 UIzck 095 R 4 jn. PUI+e 7 S 85 z 1 Wx 1 Toy. MI 3 Ub/Mee 3 My. It 60 H 2 r 2 LC 4 sp 9 CO 1 Yn 4 t. YN p. A 4 ULy 3 Dh. Fy 4 z 9 x 4 b. X+a. U+b. Symiqf 5 Jv. Sj. MXS/z. QYERW+1 fh. OKn. U 3 f. I 518 m. E 9 Gbx t. JBJJmjn. Px. Wh. Wp. SJjv. G 7 q. EAdy/Pibc. D 8 YPXn 3 NZ 7 j 1 m. U 8 Sg. Yog 9 vw. Jwz 3 fs. Ka. CS 6 AP 4 LTLN 9 ef 5 Hb/STtv. A+ow== -----END CSCI 6268 MESSAGE----- RSA signature on first two chunks

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