Encryption

Encryption

By Amir Levi and Yuval Carmel

Motivation

Ever since people were seeking for privacy Classified information Share secrets

And every time someone curious was in the way The Big Brother

By Amir Levi and Yuval Carmel

Work Method

Afterwards- we found a way to make our javascript code into Firefox Add-OnUsing:http://arantius.com/misc/greasemonkey/script-compiler

First- we used greasemonkey and firebugIn order to modify user interface

Changing user interface

By Amir Levi and Yuval Carmel

Work Method cont.

We worked by convention of:Adding buttons to

These buttonsImplements our Encryption Method

Changing user interface cont.

By Amir Levi and Yuval Carmel

Work Method cont.Encryption/Decryption Methods

We chose to encrypt using Hybrid cryptosystem methodHybrid cryptosystem combines both symmetric and asymmetric methods of encryption:

Symmetric-key cryptosystem:- In order to encrypt/decrypt mail content- Randomly generated, for every mail

Public-key (asymmetric) cryptosystem:- In order to encrypt/decrypt Symmetric-key- Generated once (add-on first use, after installation)- Send query to keys-server in order to get all addressees ‘ public-keys

(including himself)- Encrypt symmetric-key with all these public keys

By Amir Levi and Yuval Carmel

Work Method cont.

AES Algorithm was announced by National Institute of Standards and Technology(NIST) as U.S. Federal Information Processing Standards (FIPS) PUB 197 (FIPS 197) on November 26, 2001It replaced the DES Algorithm (announced in 1976) as FIPS.

AES block size is fixed, 128 bits blockand has 3 versions 128, 192, 256 indicates key size (in bits)

We chose to implement AESBecause it follows FIPSAnd also because it is fast in both software and hardware , relatively easy to implement, and requires little memoryWe follows AES-128 in CBC , PKCS#7 padding standard.

Symmetric Enc/Dec algorithm

Encryption/Decryption Methods cont.Algorithms

We used the following Enc/Dec algorithms

By Amir Levi and Yuval Carmel

We used the following Enc/Dec algorithms

Work Method cont.

RSA Algorithm The algorithm was publicly described in 1978 by Ron Rivest, Adi Shamir, and Leonard Adleman at MIT. And therefore the name of the algorithm

The RSA algorithm involves three steps: 1. Key generation2. Encryption 3. Decryption

We follows RSA PKCS#1 Version 1.5 with padding ECB, standard.Note: PKCS stands for Public Key Cryptography Standards.

Asymmetric Enc/Dec algorithm

Encryption/Decryption Methods cont.Algorithms

By Amir Levi and Yuval Carmel

The keys for the RSA algorithm are generated the following manner:1. Choose two distinct prime numbers p and q.

For security purposes, the integers p and q should be chosen uniformly at random and should be of similar bit-length. Prime integers can be efficiently found using a Primality test.

2. Compute n = pq. (used as the modulus for both the public and private keys)3. Compute the totient:

RSA Key Generation

RSA involves a public key and a private key. The public key can be known to everyone and is used for encrypting messages.Messages encrypted with the public key can only be decrypted using the private key.

.

Work Method cont.

By Amir Levi and Yuval Carmel

4. Choose an integer e such that , and e and share no divisors other than 1 (coprime).

-e is released as the public key exponent. (in our implementation e=65537)-Choosing e having a short addition chain results in more efficient encryption. Small public exponents could potentially lead to greater security risks.

5. Determine d (using modular arithmetic) which satisfies the congruence relation.

-Stated differently, ed − 1 can be evenly divided by the totient (p − 1)(q − 1).-This is often computed using the Extended Euclidean Algorithm.d is kept as the private key exponent.

The public key consists of the modulus n and the public (or encryption) exponent e. The private key consists of the modulus n and the private (or decryption) exponent d

d must be kept secret.

.

RSA Key Generation cont.

Work Method cont.

Alice transmits her public key (n,e) to Bob and keeps the private key secret. Bob then wishes to send message M to Alice.He first turns M into an integer 0 < m < n by using an agreed-upon reversible protocol known as a padding scheme. He then computes the ciphertext c corresponding to:

This can be done quickly using the method of exponentiation by squaring. Bob then transmits c to Alice.

RSA Encryption

Work Method cont.

From: BobTo: AliceContent: M

Encryption

By Amir Levi and Yuval Carmel

The last congruence directly follows from Euler's theorem when m is relatively prime to n. By using the Chinese remainder theorem(CRT) it can be shown that the equations hold for all m.This shows that we get the original message back:

Given m, she can recover the original message M by reversing the padding scheme.The above decryption procedure works because

Alice can recover m from c by using her private key exponent d by the following computation:

Now, since ,

RSA Decryption

Work Method cont.

From: BobTo: AliceContent: M

Decryption

By Amir Levi and Yuval Carmel

Work Method cont.Authenticity method

We use hash function and asymmetric cryptosystem to generate signature

The hash function we used is SHA512 from SHA2 hash function familySHA stands for Secure Hash Algorithm.

SHA hash functions are a set of cryptographic hash functions designed by the National Security Agency (NSA) and published by the NIST as a U.S. Federal Information Processing Standard.

We follows RSA PKCS #1 version 1.5 signature algorithm with SHA-512

By Amir Levi and Yuval Carmel

Authenticity method cont.

Work Method cont.

We perform the following steps in order to get signature, and verify it

Signing method1. We first digest the message M with SHA512 into Mdigested 2. Finally sender use private key d to sign on Mdigested we get S = Mdigested d mod N

Verifying method1. We use sender’s public key e to get (Mdigested d) e mod N = Mdigested mod N.2. Finally we take the original message M, digest it with SHA512 and compare it with Mdigested .

By Amir Levi and Yuval Carmel

Alice and BodAnd George Alice Bob

George

RSA Example

Bob:BobPublicKey (everyone)BobPrivateKey (keep secret)

Alice:AlicePublicKey (everyone)AlicePrivateKey (keep secret)

Bob wants to send Alice private message, m

Bob looks at AlicePublicKey (e, n) And EncryptsBob sends C to Alice on the internet

Someone may be listening…Don’t worry he sees C but cannot figure mBecause he doesn’t know AlicePrivateKey

Alice wants to decrypt Bob’s private message m

Alice looks atAlicePrivateKey (d)And Decrypts

Hey

By Amir Levi and Yuval Carmel

Bob signs on the message(after digest it) with BobPrivateKey (d) S = Mdigested d mod N

Alice wants to verify Bob’s signatureShe use BobPublicKey(e, n)Se= Mdigested

Then Alice digests decrypted m,And compares them both

Encryption with Password

Work Method cont.

FirstUser supplies password (at least 4 letters)

SecondWe use hash function in order to generate secret key for symmetric cryptosystem

ThirdWith the secret key(symmetric key) we encrypt user private key, and store it in key server.

FourthEvery time user wants to get his private key, he need to perform the following: 1. He sends to key server query to get his encrypted private key stored in server.2. He also need to enter his password, that way he generates his secret key And we decrypt the encrypted private key. 3. Finally we get the original private key

We use symmetric cryptosystem AES-128 in CBC , PKCS7 padding standard.And SHA1 hash function.By Amir Levi and Yuval Carmel

Certificate

Work Method cont.We support user X.509 Certificate, in order to bind it with his public key. Thus increase privacy and authenticity.

We choose to handle X.509 certificate in the following manner:

User who wants to increase his privacy and authenticity can supply X.509 certificate

It’ll be stored in a keys server, and user will need to supply his public and private keys in order to encrypt and decrypt.(because we cannot generate those who suits to his certificate)And we will store his keys on the key server.

Now anyone who wants to send him encrypted mail, will be able to verify and validate sender certificate.Thus get his public key, and encrypt by it.

By Amir Levi and Yuval Carmel

Work Method cont.Certificate cont.

public key certificate (also known as a digital certificate or identity certificate) is an electronic document which uses a digital signature to bind together a public key with an identity — information such as the name of a person or an organization, their address, and so forth. The certificate can be used to verify that a public key belongs to an individual.

X.509 is an ITU-T standard for a public key infrastructure (PKI) for single sign-on (SSO) and Privilege Management Infrastructure (PMI). X.509 specifies, amongst other things, standard formats for public key certificates, certificate revocation lists, attribute certificates, and a certification path validation algorithm.

By Amir Levi and Yuval Carmel

Work Method cont.

The structure of an X.509 v3 digital certificate is as follows:Certificate

VersionSerial NumberAlgorithm IDIssuerValidity

Not BeforeNot After

SubjectSubject Public Key Info

Public Key AlgorithmSubject Public Key

Issuer Unique Identifier (Optional)Subject Unique Identifier (Optional)Extensions (Optional)

...Certificate Signature AlgorithmCertificate Signature

Certificate cont.

Issuer generated the certificate

Subject use the certificateOwn the public and private keys

X.509 version3Certificate Structure

By Amir Levi and Yuval Carmel

Work Method cont.Certificate: Data: Version: 3 (0x2) Serial Number: 1 (0x1) Signature Algorithm: md5WithRSAEncryption Issuer: C=ZA, ST=Western Cape, L=Cape Town, O=Thawte Consulting cc, OU=Certification Services Division, CN=Thawte Server CA/[email protected] Validity Not Before: Aug 1 00:00:00 1996 GMT Not After : Dec 31 23:59:59 2020 GMT Subject: C=ZA, ST=Western Cape, L=Cape Town, O=Thawte Consulting cc, OU=Certification Services Division, CN=Thawte Server CA/[email protected] Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: (1024 bit) Modulus (1024 bit): 00:d3:a4:50:6e:c8:ff:56:6b:e6:cf:5d:b6:ea:0c: 68:75:47:a2:aa:c2:da:84:25:fc:a8:f4:47:51:da: 85:b5:20:74:94:86:1e:0f:75:c9:e9:08:61:f5:06: 6d:30:6e:15:19:02:e9:52:c0:62:db:4d:99:9e:e2: 6a:0c:44:38:cd:fe:be:e3:64:09:70:c5:fe:b1:6b: 29:b6:2f:49:c8:3b:d4:27:04:25:10:97:2f:e7:90: 6d:c0:28:42:99:d7:4c:43:de:c3:f5:21:6d:54:9f: 5d:c3:58:e1:c0:e4:d9:5b:b0:b8:dc:b4:7b:df:36: 3a:c2:b5:66:22:12:d6:87:0d Exponent: 65537 (0x10001) X509v3 extensions: X509v3 Basic Constraints: critical CA:TRUE Signature Algorithm: md5WithRSAEncryption 07:fa:4c:69:5c:fb:95:cc:46:ee:85:83:4d:21:30:8e:ca:d9: a8:6f:49:1a:e6:da:51:e3:60:70:6c:84:61:11:a1:1a:c8:48: 3e:59:43:7d:4f:95:3d:a1:8b:b7:0b:62:98:7a:75:8a:dd:88: 4e:4e:9e:40:db:a8:cc:32:74:b9:6f:0d:c6:e3:b3:44:0b:d9: 8a:6f:9a:29:9b:99:18:28:3b:d1:e3:40:28:9a:5a:3c:d5:b5: e7:20:1b:8b:ca:a4:ab:8d:e9:51:d9:e2:4c:2c:59:a9:da:b9: b2:75:1b:f6:42:f2:ef:c7:f2:18:f9:89:bc:a3:ff:8a:23:2e: 70:47

Certificate cont.Certificate for example

From wikipedia

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

From:http://markupsecurity.com/info/dss/keys_and_certs.html

Important note:In our implementation we support only certificate that encode with Bas64 without the tokens

-----BEGIN CERTIFICATE----------END CERTIFICATE-----

In Base64

X.509 version3Certificate Structure

By Amir Levi and Yuval Carmel

Work Method cont.

key server…

Build up key server

Work Method cont.Build up key server cont.

Work Method cont.Build up key server cont.

Mail body

By Amir Levi and Yuval Carmel

BodyThis is an encrypted Gmail

-- Start of mailencrypt --- [email protected] gjZtM5pSZ7TDqM1T8N+mqgfcVpNOgn8fLIwzdYwOND6gPR5OaJ7BUDof58RDAqBZi2Sm4dMtv4WZvONSioSL4rRJ/jJAb4CnjLSI147U3X59QASWMHDrG3M8T1DkpnmCKbuTu5aEr+kNNIF4r+q6NpzcjGKi0V06kIAtGgsuq+E= --keyEnd-- -- [email protected] h1oktl58ZjJYen5MLRWcfinHNV+uYBZO1YlIrEJgyrYbHQbURbE2h5X7frze7TuXQk95NAeUrcIWaGLckx6xt30QrT/7tVdkxB81iexJV+ywORUSyCLaNXSFghytxLQUwv9shyhJwfCQSvl6GHd0XtW7OVCnhowRk4/spmpp69k= --keyEnd-- [email protected] AgA2gX2zbHuqjq+yA6eKB0MV5b7Lyw8aqLVO/kRARufY18BqEUI+PNkEWuvL5AzdDtzFKuJbhikpjqFbAFfW/5J8ATRrbKCBMbfFF+ETaDyR/SKe/KXLqtauGe/5jLrK8b73nx4Twl990ftj8pEj1wYHup2w8i159a5iG65rN7M= --keyEnd– :40 5e 1e 5b 4d ed 30 18 21 56 1d 46 04 2c d3 c7$2e bc ab fa 08 04 b8 d8 1a 62 55 df e2 3f 9c b4$4a fe fd 8b 98 6c fe 33 02 dc b0 2e ae 6f 25 96$ac 46 2d 48 ca fd 8e 07 e7 73 19 87 36 3b 7c ad$7f c9 14 13 0a ed bf 31 37 d5 fa 04 7d 63 15 e6$fa 35 94 58 f5 1a 83 bb 29 de 94 68 56 fc 87 ec$34 82 4d b1 46 44 4f 56 51 cf 7d 95 e9 3e 1a 6c --- End of mailencrypt ---

SubjectEncrypted Gmail

Mail body cont.When pressing on encrypt, the following mail for encryption body is produced:Symmetric Key for all addressees(including himself)

Encrypted by their public key(each one)Separated by Delimiters:--addressee– “key” –keyEnd--

By Amir Levi and Yuval Carmel

Delimiter “:” to denote the mail contentMail content (subject and body separated by delimiters ) structure:--start of subject– Mail Subject example--end of subject-- Mail Body example

Mail content Encrypt by symmetric key

After we’ve got, Symmetric key encrypted for all addressee(including himself), by theirPublic keysAnd also mail content encrypted by symmetric key.We encapsulate them using delimiters-- Start of mailencrypt ---Symmetric Key encrypted for addresseeMail content encrypted--- End of mailencrypt ---

Mail body cont.

DecryptEncrypt and send

By Amir Levi and Yuval Carmel

Questions ?

By Amir Levi and Yuval Carmel