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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.
2022-07-29, 40088👍, 26💬

💬 2022-07-13 itsMeAbhi: Well explained.

💬 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

(More comments ...)

EC Cryptography Tutorials - Herong's Tutorial Examples
This EC (Elliptic Curve) cryptography tutorial book is a collection of notes and sample codes written by the author while he was learning cryptography technologies himself. Topics include rule of chord and point addition on elliptic curves; Abelian groups with additive/multiplicative notations; EC a...
2022-07-27, 3075👍, 8💬

💬 2022-07-27 Aman: Perfect book to help my 'encoding' project. Thank you!

💬 2020-06-23 Herong: Chris, contact me by email. I will send you a PDF copy. Thanks for your comment.

💬 2020-06-22 chris: Sorry for fuss. Bought this ebook on google. bad idea. Should have not done that and just got the physical book or maybe ebook o...

💬 2019-01-01 Yale: Thank you!

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.
2022-07-11, 606👍, 2💬


💬 2020-11-07 abc: Ravana

First 8336 Hex Digits of PI
This section provides first 8336 hex digits of constant PI, 3.1415927..., needed for Blowfish encryption algorithm.
2022-06-26, 6555👍, 11💬

💬 2019-04-28 Herong: 8336 Hex Digits. Thanks.

💬 2019-04-26 Harry: Do you mean 8336 digits

💬 2016-10-31 Andres: cool

💬 2016-04-07 Tamas Losonczi: This is great

💬 2016-03-15 Bogdan: Thanks!

(More comments ...)

Blowfish - 8-Byte Block Cipher
This chapter provides tutorial examples and notes about Blowfish block cipher. Topics include Blowfish encryption and decryption algorithm; Blowfish sub-key generation schema, Blowfish algorithm implementation in Java.
2022-06-21, 574👍, 3💬

💬 2022-06-21 sad: hello world

💬 2019-12-16 gio: i love you

DES Key Schedule (Round Keys Generation) Algorithm
This section describes DES (Data Encryption Standard) algorithm - A 16-round Feistel cipher with block size of 64 bits.
2022-06-06, 13230👍, 12💬

💬 2022-06-06 hello: <script> alert("Hello! I am an alert box!"); </script>

💬 2018-02-24 Herong: hema, values in the pc-2 table are pre-defined by the algorithm. They are not calculated.

💬 2018-02-23 hema: i understood pc-1 table can you pls guide to calculate manually pc-2 table in des algorithm.

💬 2017-10-24 Herong: QuAI, you are right those bits are not used in the Permuted Choice 1 (PC1) table.

💬 2017-10-19 QuAl: And forget about bits 8, 16, ..., 64 of initial кey K! Those bits for parity check only (see FIPS 46-3)

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What Is DER (Distinguished Encoding Rules) Encoding?
This section describes the DER (Distinguished Encoding Rules) - A binary format of encoding a data value of any data types including nested data structures.
2022-06-03, 21139👍, 9💬

💬 2018-10-29 Thanks!: meaningful comments.

💬 2017-03-15 noname: thanks

💬 2016-01-25 Dev: hello

tinyec - Python Library for ECC
This chapter provides tutorial notes on 'tinyec' Python library for ECC. Topics include installing 'tinyec'; creating ec.Curve objects, performing point addition and scalar multiplication.
2022-05-16, 253👍, 2💬

💬 2022-05-16 maria: hola mi mundo bonito

Elliptic Curve Geometric Properties
This section describes two geometric properties of an elliptic curve: horizontal symmetry and 3 intersections or less with straight lines.
2022-05-15, 111👍, 1💬

What Is an Elliptic Curve?
This section describes what is elliptic curve - A set of 2 dimensional points of (x, y) that satisfy the y*y = x*x*x + a*x + b equation with given values of a and b.
2022-05-15, 107👍, 1💬

ECES (Elliptic Curve Encryption Scheme)
This chapter provides tutorial notes on ECES (Elliptic Curve Encryption Schema). Topics includes ECES plaintext encryption and ciphertext decryption processes; using Crypto.Cipher.AES module to test ECES.
2022-05-06, 167👍, 1💬

💬 2022-05-06 Mk: Hello how r you?

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.
2022-05-06, 6217👍, 7💬

💬 2022-04-23 Shivam: Please provide the code for the same

💬 2021-12-23 x: 5

💬 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?

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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.
2022-04-12, 2256👍, 5💬

💬 2022-04-12 Yesssuuh: Gang way

💬 2017-11-10 Anonymous: LOLZZZ

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.
2022-03-29, 657👍, 3💬

💬 2022-03-29 asdasd: I hate it enough to like it. That being said, as we discussed before probably have a look at the difficulty rating of this vs th...

💬 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...

"openssl pkcs8" Converting Keys to PKCS#8 Format
This section provides a tutorial example on how to convert a private key file from the traditional format into PKCS#8 format using the 'openssl pkcs8' command. Keys can still be encoded with DER or PEM with or without DES encryption in PKCS#8 format.
2022-03-08, 14437👍, 2💬

💬 2022-03-08 randomn: random123

💬 2016-04-12 Nishant Desai: Does anyone knows any library by which i can execute openssl pkcs8 -topk8 -in openssl_key.pem -inform pem -out openssl_key_pk8_e...

Abelian Group on Elliptic Curve
This section demonstrates that an Abelian Group can be defined with all points on an elliptic curve with the 'rule of chord' operation.
2022-03-02, 106👍, 1💬

PHP Implementation of DES - mcrypt
This chapter provides tutorial examples and notes about PHP implementation of DES. Topics include introduction of mcrypt library; mcrypt encryption functions; DES encryption and decryption test program and test result.
2022-02-24, 2767👍, 5💬

💬 2018-12-22 Hari: Hello

💬 2016-01-02 sivaprakash: nice

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.
2021-12-27, 10759👍, 6💬

💬 2021-12-27 Azul: Why do you want me to write things like that?

💬 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 ):

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, 15680👍, 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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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, 6422👍, 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, 11898👍, 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, 6172👍, 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, 33751👍, 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...

PDF Printing Version: Cryptography Tutorials
Information on how to obtain the PDF version of this book for printing.
2021-07-27, 8109👍, 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 ...)

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