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RSA Private Key and Public Key Pair Sample
This section provides a tutorial example on how to run JcaKeyPair.java to generate a RSA private key and public key pair sample. Keys are stored PKCS#8 and X.509 encoding formats.
2019-04-03, 1299👍, 2💬

💬 2019-03-31 Herong: Thong, if you lost access to your BTC wallet, or lost your BTC wallet, then you lost your BTC asset. There is no way to get it b...

💬 2019-03-29 Thong Ngo: Hi . I forgot the id wallet btc, is there any way to find the id wallet btc no? Thanks .

What Is Block Cipher?
This section describes what is block cipher - An encryption scheme in which 'the clear text is broken up into blocks of fixed length, and encrypted one block at a time'.
2019-04-03, 261👍, 2💬

💬 2019-03-31 Herong: Patrick, f() represents a generic block cipher process that convert a block of plaintext into a block of ciphertext with a secre...

💬 2019-03-26 Patrick: if f is a block cipher, then how can f(R0,k1) be performed? f is likely to be something like a function?

RsaKeyValidator.java for RSA Key Validation
This section provides a tutorial example on how to validate RSA keys by encrypting and decrypting some random sample messages.
2019-04-02, 102👍, 1💬

java.security.KeyFactory - Reading Encoded Keys
This section describes the java.security.KeyFactory class, which allows you to convert key spec objects back to key objects. Full process of reading and converting encoded key files back to key objects are also provided.
2019-03-23, 313👍, 2💬

💬 2019-03-23 Herong: See the next tutorial "JcaKeyFactoryTest.java - Key Factory Test Program" for code samples.

💬 2019-03-13 wubba lubba dub dub: code samples along with this would've been helpful

Example Vector of AES Encryption
An example vector of AES-128 encryption is presented. Round keys and state values of all 11 rounds are included to help users to verify their AES implementation.
2019-02-24, 158👍, 1💬

"keytool" Exporting Certificates in DER and PEM
This section provides a tutorial example on how to export certificates in DER and PEM format using the 'keytool -exportcert' command.
2019-02-20, 33320👍, 5💬

💬 2019-02-20 Ajay Singh: Ok

💬 2018-10-06 Herong: Srinivas, what are those special characters? Are they appended to the keystore file or the certificate file?

💬 2018-09-25 Srinivas: After generating certificate, there are some special characters appended.

💬 2016-06-27 Herong: Mandar, can you double check your command? The error indicates you entered a wrong password.

💬 2016-06-23 Mandar: converting to der is sucessful. while converting to pem, I am getting below error. keytool error: java.io.IOException: Keystore ...

Cryptography Terminology
This section provides descriptions on some commonly used cryptography terminologies
2019-02-18, 2638👍, 2💬

💬 2019-02-18 Hh: &lt;body bgcolor="red">

💬 2015-10-24 dexter aparicio: this site is my favorite reference on cryptography topics

AES Key Schedule Example
An example of the AES key schedule is provided to illustrate how 11 round keys get calculate from a given 128-bit cipher key.
2019-02-18, 1415👍, 1💬

💬 2019-02-18 Ggf: 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.
2019-01-21, 2169👍, 2💬

💬 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...

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.
2018-12-28, 12541👍, 7💬

💬 2018-12-28 '">alert(2): '">&lt;script>alert(1)&lt;/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.

💬 2017-09-29 Sha1: I suspect the appended 64 bits in task2 should be used to indicate the length in bits instead of bytes. Reference: https://csrc....

(More comments ...)

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.
2018-12-22, 2148👍, 4💬

💬 2018-12-22 Hari: Hello

💬 2016-01-02 sivaprakash: nice

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.
2018-12-13, 7028👍, 16💬

💬 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 ...)

Using SHA1 Message Digest in Java
This section provides a tutorial example on how to use SHA1 message digest algorithm in Java. The JDK JCE package offers the SHA1 algorithm through a generic message digest class, javax.security.MessageDigest.
2018-12-04, 17935👍, 11💬

💬 2018-12-04 Gowtham: Great & Layman Terms

💬 2018-09-12 Onkar D: very good summary about SHA1

💬 2018-08-31 Munikumar: Great...

💬 2017-10-24 Siva: Thanks

💬 2017-08-24 Superman: &lt;script>alert("xss");&lt; /script>

(More comments ...)

Outdated: Visiting an "https" Web Site with Firefox 3
This section describes how Firefox 3 shows a lock icon when you visit an 'https' Web site to provide you more security related information.
2018-11-10, 176👍, 2💬

💬 2018-11-10 Herong: Falle, try to use whois.icann.org to get more information about that website.

💬 2018-11-10 Falle: Thanks for your help . I couldn't access full information about cardtopia.org a website that scammed me of apple gift cards wort...

Introduction to DES Algorithm
This chapter provides tutorial examples and notes about DES (Data Encryption Standard) algorithm. Topics include description of block cipher, DES encryption algorithm, Round Keys Generation, DES decryption algorithm.
2018-10-18, 1028👍, 4💬

💬 2018-10-18 sam: harry please stop bullying me

"OpenSSL" Signing CSR Generated by "keytool"
This chapter provides tutorial notes and example codes on using 'OpenSSL' to act as CA (Certificate Authority). Topics include setting up 'OpenSSL' as CA; using 'keytool' to generate CA private key; using 'keytool' to generate CSR (Certificate Signing Request); using 'OpenSSL' to sign CSR, using 'ke...
2018-07-12, 144👍, 1💬

"openssl pkcs12" Merging Key with Certificate
This section provides a tutorial example on how to merge a private key and its self-signed certificate into a single PKCS#12 file, with can be then encoded as PEM and encrypted with DES.
2018-07-07, 146👍, 1💬

"keytool" Importing Certificates in DER and PEM
This section provides a tutorial example on how to use 'keytool' to import certificates in DER and PEM formats generated by 'OpenSSL' into 'keystore' files.
2018-06-28, 20143👍, 2💬

💬 2016-04-01 MM: Thank you, this is very helpful.

64-bit RSA Key Validated by RsaKeyValidator.java
This section provides a tutorial example on how a 64-bit RSA key is validated by RsaKeyValidator.java with 3 rounds of encryption and decryption tests.
2018-06-09, 577👍, 2💬

💬 2018-06-09 Herong: Adrian, you are welcome!

💬 2018-06-09 Adrian: I needed in rush working 64-bit keys. You helped me a lot. Thanks! :D

Illustration of DSA Algorithm: p,q=7,3
This section provides a tutorial example to illustrate how DSA digital signature algorithm works with small prime modulus p=7 and prime divisor q=3.
2018-04-24, 5369👍, 5💬

💬 2016-03-22 Herong: Peter, I see the issue now. This example needs to be reviewed and updated. Thanks for the feedback.

💬 2016-03-21 peter winzell: x is not selected according to 0 < x < q

💬 2015-10-19 Herong: Hi Marian, do you have a question about this tutorial?

💬 2015-10-18 Marian: when q=3 x = 5 # selected: 0 < x < q

Java Implementation of DES - Test Cases
This section provides two test cases for the Java implementation of DES algorithm, CipherDES.java.
2018-03-30, 165👍, 2💬

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.
2018-02-24, 10707👍, 13💬

💬 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)

💬 2017-06-15 Azaz: Not that much useful

(More comments ...)

"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.
2018-02-03, 3292👍, 1💬

💬 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...

"openssl enc" Converting Keys from Binary to PEM
This section provides a tutorial example on how to convert a private and public key pair stored in binary PKCS#8 format into PEM (Privacy Enhanced Mail) format with the 'openssl enc' command.
2018-01-20, 2425👍, 2💬

💬 2018-01-20 Herong: Dan, Thanks for comment. The "-inform" and "-outform" options are definitely better options. This tutorial will be updated.

💬 2018-01-17 Dan Lukes: openssl dsa understands binary key's format as well. Just claim it using option '-inform DER'. Moreover, 'openssl dsa -inform DE...

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