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What Is PKCS5Padding?
This section describes what is PKCS5Padding - a schema to pad cleartext to be multiples of 8-byte blocks.
2021-11-23, 35129👍, 18💬

💬 2021-09-10 me: hello

💬 2021-08-09 meaningful comment: Let (a,b)=(10,10), what is a+b?

💬 2021-08-07 kane: here forever

💬 2021-07-25 shivam tyagi: thanks

💬 2021-06-17 My name: meaningful comments

(More comments ...)

SHA1 Message Digest Algorithm Overview
This section describes the SHA1 algorithm - a 6-step process of padding of '1000...', appending message length, preparing 80 process functions, preparing 80 constants, preparing 5 word buffers, processing input in 512 blocks.
2021-10-25, 14253👍, 8💬

💬 2021-10-25 kareem: karee

💬 2018-12-28 '">alert(2): '"><script>alert(1)</s cript>

💬 2017-10-26 Herong: Jamal, w(0), ..., w(15) are initial values. w(16), ..., w(79) are used on the left side of the assignment operator to store stor...

💬 2017-10-25 Y. Jamal: Hi, we have w(0), w(1),....w(15) how come in the For loop we have W(t) and t goes from 16 to 79. something is not right.

💬 2017-09-29 Herong: I don't think it takes the length of bits. But I will double check it.

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Certificate in PEM Format
This section describes what is certificate PEM (Privacy Enhanced Mail) format - A format uses PEM idea to convert a certificate in DER format to a message of printable characters. The conversion uses the Base64 encoding.
2021-10-21, 8693👍, 5💬

💬 2021-10-21 kaka: kaka

💬 2020-02-23 Herong: Mark, if your certificate is signed by your own CA, put it on the Apache server together with the CA certificate to test. Other ...

💬 2020-02-17 mark scorfield: Hi i have a pem certificate x509 that i would like to share against my own certificate signing authority , what is the best way ...

💬 2016-03-30 Herong: Bcbin, why don't you post your question here? Maybe others can help you too. Or send me an email directly.

💬 2016-03-27 bcbin: my name is bcbin, my email is bcbin@yahoo.com. please connecting me. i need you help ):

Subkeys of 3DES Encryption
Hi Doc, I have subkeys recovered through DPA. Can 3DES.c be modified to accept these subkeys as inputs for a cryptographic operation? Alternatively, can the main 3DES key be reverse generated from the subkeys? Thanks. jeffrey****alis@gmail.com
2021-10-15, 5887👍, 2💬

💬 2021-10-15 bddsm: This section provides a tutorial example

💬 2015-07-22 Herong: Hi Jeffrey, Which 3DES.c are you referring to? Can you tell me where I can see the code?

MD5 Message Digest Algorithm Overview
This section describes the MD5 algorithm - a 5-step process of padding of '1000...', appending message length, dividing as 512-bit blocks, initializing 4 buffers, and 4-round of hashing each block.
2021-10-04, 11415👍, 7💬

💬 2016-11-21 this is a burner: concise and accurate, thanks

💬 2016-09-26 brijesh gupta: its helpful

💬 2016-06-17 Ampera: Makasih

"OpenSSL" Generating CA's Private Key
This section provides a tutorial example on how to use OpenSSL to generate a RSA private key of 2048 bit long with OpenSSL. This key will be used as the CA's private key and must stored securely in a file with password protection.
2021-09-24, 4596👍, 2💬

💬 2021-09-24 samiam: Proc-Type: 4,ENCRYPTED DEK-Info: DES-CBC,65D5EB070215060E 85d+v8K1kPwCgFarsMD+5FpVs6doCZPeCjMr rWzyym5wIKHKqV8tfAjO...Z2JBXMGxAV...

💬 2018-02-03 atomic.kidd: most Excellent Herong for this sharing of excellent Informations. Even the openssh documentation is not up to date nor as accura...

Cryptography Tutorials - Herong's Tutorial Examples
This cryptography tutorial book is a collection of notes and sample codes written by the author while he was learning cryptography technologies himself. Topics include AES, blowfish, certificate, cipher, decryption, DES, digest, encryption, keytool, MD5, OpenSSL, PEM, PKCS#8, PKCS#12, private key, p...
2021-08-28, 32147👍, 7💬

💬 2017-06-17 Herong: Neil, I will try my best. Thanks for the comment.

💬 2017-06-14 Neil Shrestha-Birtch: It helped me! thanks for keeping this resource up.

💬 2016-01-11 Sandy: Good job Dr Herong Yang!

💬 2015-11-07 Herong: My Facebook Like count is not going up. ☹ Maybe there is not that many active Facebook users out there as we thought...

Cleartext Block Size for RSA Encryption
This section discusses what is the most efficient block size when dividing a Cleartext message into blocks for RSA public encryption. The suggested block size is 'floor((x-1)/8)', where 'x' is the RSA key size, or the key modulus bit length.
2021-08-18, 370👍, 2💬

💬 2021-08-18 test: Obviously, using 200-bytes as the block size is much more efficient than 1-byte block size. This means the higher block size, th...

PDF Printing Version: Cryptography Tutorials
Information on how to obtain the PDF version of this book for printing.
2021-07-27, 7823👍, 36💬

💬 2021-07-27 attila: thanks

💬 2019-07-04 aladdin: thanks

💬 2018-10-20 Herong: bachi, thanks for sharing your comment.

💬 2018-10-13 bachi: I like how you composed your content. I like how you explain the DES algorithm

💬 2018-09-12 aaa: thanks

(More comments ...)

What Is Cryptography?
This section describes what is cryptography - The study of techniques related to all aspects of data security.
2021-04-25, 2784👍, 6💬

💬 2021-04-25 jlong: thanks

💬 2017-02-18 gabu: ggoodd

💬 2016-11-17 mohamed: yes

💬 2015-10-20 Herong: Hi Ian, the Rail Fence cipher is very simple example of encryption we can do manually. See the Transposition cipher page at wiki...

💬 2015-10-19 Ian T. Lee: Can you give me a simple example of how to do cryptography manually?

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AES Standard Decryption Algorithm
The standard decryption algorithm of the AES-128 encryption is provided. It is a straightforward reverse of the encryption algorithm.
2021-04-25, 114👍, 1💬

"keytool" and "keystore" from JDK
This chapter provides tutorial notes and example codes on 'keytool' and 'keystore'. Topics include introduction of 'keytool' and 'keystore'; using 'keytool' to generate private keys, generate self-signed certificates, export and import certificates.
2021-04-23, 195👍, 1💬

💬 2021-04-23 chanho.song: wow. I'm Korean. Thank u so much.

How Secure Is RSA Algorithm?
This section discusses the security of RSA public key encryption algorithm. RSA private key is not 100% secure. But if the private key uses larger value of n = p*q, it will take a very long time to crack the private key.
2021-03-03, 1942👍, 3💬

💬 2017-11-10 Anonymous: LOLZZZ

What Is tinyec
This section introduces what is tinyec - a tiny library to perform arithmetic operations on elliptic curves in pure Python.
2021-03-02, 109👍, 1💬

Illustration of DSA Algorithm: p,q=23,11
This section provides a tutorial example to illustrate how DSA digital signature algorithm works with small prime modulus p=23 and prime divisor q=11.
2021-01-09, 1528👍, 6💬

💬 2021-01-09 Flying Horse: Hello Dr Yang, My verification scheme is as follows lhs = (r**s mod p)mod q rhs = ((g**h mod p)*(y**r mod p)) mod q If lhs = rhs...

💬 2021-01-08 Herong: Flying, give us an example to show that this verification scheme is not working?

💬 2021-01-07 Flying Horse: Hello Dr Yang, this is a very helpful tutorial. I am trying a different verification scheme for DSA signature. Unfortunately, it...

💬 2020-06-22 Filip: Very helpful, thanks!

💬 2020-02-24 Herong: Sanjay, hash value of 3 was used as a simple example, not calculated.

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What Is DSA (Digital Signature Algorithm)?
This section describes the DSA (Digital Signature Algorithm) algorithm, which consists of 2 parts: generation of a pair of public key and private key; generation and verification of digital signature.
2021-01-08, 32086👍, 17💬

💬 2021-01-08 Herong: Abigail, you are welcome!

💬 2021-01-06 Abigail: Thank you so much, just what I needed for my university assignment!

💬 2020-12-05 Herong: Donghua, h is any integer you pick to help generating g.

💬 2020-12-04 Donghua: What's the h means in step three. How to calculate it?

💬 2018-08-29 Shawn: Thanks for the detailed explanation.

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Converting Secret Keys to and from Byte Arrays
This section provides a quick introduction of the SecretKeySpec class and the KeySpec interface. They can be used to convert secret keys into byte arrays to store them in external files.
2020-11-23, 13589👍, 5💬

💬 2019-04-22 xyz: $9$RTHhSlWL7VsguO7dbw4oiHqf6CuOIRhyl K4JGDq.TQF/OIcyeLXNbsPTz3CAW8X

💬 2018-10-20 Herong: Marco, I just did a Google translation on your comment: "I wonder what all this could be". Are you trying to ask a question?

💬 2018-10-16 Marco: mi chiedo che cosa potrebbe essere tutto questo

💬 2015-11-03 cpp: hello

Illustration of RSA Algorithm: p,q=5,7
This section provides a tutorial example to illustrate how RSA public key encryption algorithm works with 2 small prime numbers 5 and 7.
2020-11-22, 4818👍, 4💬

💬 2020-11-22 Herong: fab, as shown in the tutorial, the modulus is 35. The encryption key (public key) is 5, and the decryption key (private key) is ...

💬 2020-11-15 fab: Construct an example of the RSA scheme as follows. The two primes to be used for the modulus N are 5 and 7. What is (N)? Confir...

💬 2019-01-21 Herong: someone, why 35 and 5 must be coprime numbers?

💬 2019-01-16 someone: >Compute n = p*q: n = 5*7 = 35 >Compute m = (p-1)*(q-1): m = 4*6 = 24 >Select e, such that e and m are coprime numbers: e = 5 35...

DES Algorithm Java Implementation
This chapter provides tutorial examples and notes about DES algorithm implementation in Java language. Topics include an example Java implementation of DES encryption and decryption algorithm; test cases of single block cleartext and ciphertext.
2020-11-11, 7277👍, 17💬

💬 2018-12-13 syed zia ur rehman: i realy like your link

💬 2017-10-15 Herong: CipherDES.java also works as a decryption program. Try it by running "java DesCipher decrypt keyFile input output".

💬 2017-10-09 aa: thanks, but where i can find DES decryption

💬 2017-10-09 Denys: thx

💬 2017-04-23 aa: thanks

(More comments ...)

EC Private and Public Key Pair
This section introduces what is EC (Elliptic Curve) key pair - a pair of private key and public key constructed from a given subgroup generator in a given elliptic curve group.
2020-11-07, 330👍, 1💬

💬 2020-11-07 abc: Ravana

What is ECB (Electronic CodeBook) Operation Mode?
This section describes what is ECB (Electronic CodeBook) Operation Mode - each plaintext block is encrypted independently without any input from other blocks.
2020-10-18, 4629👍, 4💬

💬 2020-10-18 Herong: donjo, there is no real applications that use the ECB mode.

💬 2020-10-16 donjo dumdum: What is application of ECB mode operation

💬 2016-01-10 Todd: Thanks!

Geometric Introduction to Elliptic Curves
This chapter provides a geometric introduction of elliptic curves and the associated addition operation. Topics includes what is an elliptic curve and its geometric properties; geometric algorithm defining an addition operation; infinity point or identity element; commutativity and associativity of ...
2020-09-12, 299👍, 1💬

💬 2020-09-12 NA: NA

"OpenSSL" Generating Certificates in DER and PEM
This section provides a tutorial example on how to generate certificates in DER and PEM formats using 'OpenSSL'.
2020-09-09, 5199👍, 2💬

💬 2020-09-09 test: test

Visiting a "https" Web Site with Chrome
This section describes how Google Chrome 24 shows a lock icon when you visit an 'https' Web site to provide you more security related information.
2020-07-02, 470👍, 2💬

💬 2020-07-02 Koshal Pravin jangale: Nice

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