1. email or call for office visit, or call Kathy Cheek, 404 894-5696
ECE-6612
Prof. John A. Copeland
fax
Office: Centergy Room 5138
or call for office visit, or call Kathy Cheek,
Chapter 4b - X.509 Authentication

2. X.509 Authentication Service
• An International Telecommunications Union (ITU) recommendation (versus “standard”) for allowing computer host or users to securely identify themselves over a network.
• An X.509 certificate purchased from a “Certificate Authority” (trusted third party) allows a merchant to give you his public key in a way that your Browser can generate a session key for a transaction, and securely send that to the merchant for use during the transaction (padlock icon on screen closes to indicate transmissions are encrypted).
• Once a session key is established, no one can “high jack” the session (for example, after your enter your credit card information, an intruder can not change the order and delivery address).
• User only needs a Browser that can encrypt/decrypt with the appropriate algorithm, and generate session keys from truly random numbers.
• Merchant’s Certificate is available to the public, only the secret key must be protected. Certificates can be cancelled if secret key is compromised.

3. Raw “Certificate” has user name, public key, expiration date, ...
CA’s Secure Area
Generate hash code
of Raw Certificate
Raw
Cert.
MIC
Hash
Encrypt hash code with CA’s private key to form CA’s signature
Signed
Cert.
Signed Certificate
Recipient can verify signature using CA’s public key.
Certificate Authority generates the
“signature” that is added to raw
“Certificate” 3

4. 4

5. Information Provided by Browser about a Certificate
This Certificate belongs to:
investing.schwab.com
trading subnet a 1199
Charles Schwab & Co., Inc.
Phoenix, Arizona, US
This Certificate was issued by
Secure Server Certification Authority
RSA Data Security, Inc. US
Serial Number: 6B:68:2F:3B:FD:8A:46:73:04:33:10:8A:32:1E:47:5B
This Certificate is valid from Wed Nov 03, 1999 to Thu Nov 02, 2000
Certificate Fingerprint:
4B:80:C6:C5:2D:63:14:E7:6F:50:BD:16:39:3C:96:FD 5

6. Certificates Can Be Deleted (and Added)
Are you sure that you want to delete this Site Certificate?
This Certificate belongs to:
endor.mcom.com
Netscape Communications Corp. US
This Certificate was issued by:
rootca.netscape.com
Information Systems
Netscape Communications Corporation
Serial Number: 01:77
This Certificate is valid from Thu May 15, 1997 to Tue Nov 11, 1997
Certificate Fingerprint:
06:BF:60:88:D9:E7:59:BF:3A:35:74:33:28:8E:26:F6 6

7. X.509 Chain of Authentication
CA<<A>> = CA {A’s id and information}
X<<A>> = certificate of A “signed” by X
To authenticate X<<A>>, you must get the public key of X from a trusted source, such as Z - your own CA. ( Z<<X>>)
Z in turn may have to get X’s certificate from a higher level CA.
Ultimately there must be an “Authentication Tree” of CA’s so that a user can work up the tree (from Z) and back down to the issuer of the certificate in question, X. 7

8. Chain of Authentication
In practice, there is no single top-level Certificate Authority (CA), only a group of CA’s that each Browser vendor deems fit to include in the installation program.
X.509
Chain of Authentication 8

9. Certificate Authorities in Mozilla (2006)9

10. Making a DES Key from a Password or Phrase
password, n 7-bit ASCII characters (little endian - least significant bit first)
flattened bit stream (7 x n bits)
fanfold into 56 bits
bitwise XOR
64-bit key
Every eighth bit is a parity bit 10

11. Programs Available from
hextext.c - allows you to view files in both hex and ascii formats.
char_count.c - shows the number of different characters in a file, computes the character entropy.
To use, you must first compile them. On a UNIX or LINUX:
gcc hextext.c -o hextext (the executable file is “hextext”)
./hextext for help
./hextext filename file and max. bytes
./hextext filename | less see one screen at a time
gcc char_count.c -lm -o char_count (note the “-lm” for math library)
./char_count filename
If “gcc” is not available, try “cc”.
“less” is better than “more” (use “^u” to back up, “space” for next page). 11

12. Output from ‘hextext’ 12 Maximum Lines (p_limit) value: 30
Input File is s100.raw
Byte No HEX VALUES TEXT
0: d4c3 b2a : d...
20: e ead e e : .....DH8....N...N...
40: da3 :
60: f11 16fc f :
80: c 90c7 061a : .B...5.,
100: : ...
120: e fd a400 : u......DH8!...r.....
140: f00 : P..
160: 308c acf 4000 fc11 d :
180: f a8a 061a : .X0/.5....z
200: :
220: c00c a1ce : edu
Lines: 30, hextext.c by John Copeland 12/5/99 12

13. Output from ‘char_count’
$ ./char_count char_count.c
char_count vers File is char_count.c
No. Char.s to EOF = 7396, No. Lines = 183
Occurrence of Single Characters
0 | ^P- 0 | | | P | ` | p- 154
^A- 0 | ^Q- 0 | ! | | A | Q | a | q- 0
^B- 0 | ^R- 0 | " | | B | R | b | r- 316
^C- 0 | ^S- 0 | # | | C | S | c | s- 243
^D- 0 | ^T- 0 | $ | | D | T | d | t- 263
^E- 0 | ^U- 0 | % | | E | U | e | u- 108
^F- 0 | ^V- 0 | & | | F | V | f | v- 45
^G- 0 | ^W- 0 | ' | | G | W | g | w- 8
^H- 0 | ^X- 0 | ( | | H | X | h | x- 31
^I- 18 | ^Y- 0 | ) | | I | Y | i | y- 64
^J- 247 | ^Z- 0 | * | : | J | Z | j | z- 4
^K- 0 | ^[- 0 | | ; | K | [ | k | {- 24
^L- 0 | ^\- 0 | , | < | L | \ | l | |- 4
^M- 0 | ^]- 0 | | = | M | ] | m | }- 24
^N- 0 | ^^- 0 | | > | N | ^ | n | ~- 0
^O- 0 | ^_- 0 | / | ? | O | _ | o | - 0
Occurrence of Single Characters - Sorted
-3488 | "- 75 | F- 13 | `- 0 | | A | C | E0- 0 13

14. 14 Occurrence of Single Characters - Sorted
-3488 | "- 75 | F- 13 | `- 0 | | A | C | E0- 0
n- 342 | | P- 12 | Q- 0 | | A | C | E1- 0
i- 338 | y- 64 | | ^B- 0 | | A | C | E2- 0
r- 316 | | #- 9 | ^C- 0 | | A | C | E3- 0
e- 296 | b- 48 | D- 8 | $- 0 | | A | C | E4- 0
t- 263 | v- 45 | w- 8 | ^E- 0 | | A | C | E5- 0
c- 262 | | U- 8 | ^F- 0 | | A | C | E6- 0
/- 255 | <- 35 | k- 6 | G- 0 | | A | C | E7- 0
^J- 247 | %- 32 | :- 5 | H- 0 | | A | C | E8- 0
s- 243 | x- 31 | B- 5 | ^A- 0 | | A | C | E9- 0
*- 232 | >- 31 | M- 5 | J- 0 | 8A- 0 | AA- 0 | CA- 0 | EA- 0
o- 213 | | |- 4 | ^K- 0 | 8B- 0 | AB- 0 | CB- 0 | EB- 0
a- 202 | \- 29 | ^- 4 | ^L- 0 | 8C- 0 | AC- 0 | CC- 0 | EC- 0
;- 193 | N- 29 | z- 4 | ^M- 0 | 8D- 0 | AD- 0 | CD- 0 | ED- 0
p- 154 | _- 27 | | ^N- 0 | 8E- 0 | AE- 0 | CE- 0 | EE- 0
f- 154 | I- 27 | Y- 2 | ^O- 0 | 8F- 0 | AF- 0 | CF- 0 | EF- 0
l- 152 | E- 27 | @- 1 | ^P- 0 | | B | D | F0- 0
m- 123 | | &- 1 | q- 0 | | B | D | F1- 0
=- 121 | T- 25 | K- 1 | ^R- 0 | | B | D | F2- 0
(- 116 | {- 24 | !- 1 | ^S- 0 | | B | D | F3- 0
)- 116 | }- 24 | ^H- 0 | ^T- 0 | | B | D | F4- 0
,- 109 | L- 22 | 0 | ^U- 0 | | B | D | F5- 0
u- 108 | '- 18 | ^V- 0 | V- 0 | | B | D | F6- 0
| ^I- 18 | ^G- 0 | W- 0 | | B | D | F7- 0
[- 104 | | ^X- 0 | X- 0 | | B | D | F8- 0
]- 102 | O- 17 | ?- 0 | ^Y- 0 | | B | D | F9- 0
h- 100 | | ^Z- 0 | Z- 0 | 9A- 0 | BA- 0 | DA- 0 | FA- 0
| C- 16 | ^W- 0 | ^[- 0 | 9B- 0 | BB- 0 | DB- 0 | FB- 0
d- 95 | A- 16 | ^D- 0 | ^\- 0 | 9C- 0 | BC- 0 | DC- 0 | FC- 0
g- 78 | R- 14 | ^Q- 0 | ^]- 0 | 9D- 0 | BD- 0 | DD- 0 | FD- 0
| S- 14 | ^^- 0 | ~- 0 | 9E- 0 | BE- 0 | DE- 0 | FE- 0
| j- 13 | ^_- 0 | bs- 0 | 9F- 0 | BF- 0 | DF- 0 | FF- 0
Entropy is 4.5 bits/byte. Maximum character-wise compression = 56.5 %
No. Char.s > 127 (not ASCII text) = 0, 0 % 14