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"keytool" Importing CA's Own Certificate
This section provides a tutorial example on how to import CA's certificate generated by 'OpenSSL' into a 'keystore' file using 'keytool'
2016-10-20, 312👍, 2💬

💬 2016-10-20 Herong: Akhtar, AES256 encryption does not require any certificates. It requires a secret AES key, see Introduction to AES (Advanced Enc...

💬 2016-10-19 Akhtar: I have also a certificate file (.cer) .I did the same procedure to import in to mykey store and got .jks file but, now i want to...

"OpenSSL" Viewing Certificates in DER and PEM
This section provides a tutorial example on how to use 'OpenSSL' to view certificates in DER and PEM formats generated by the 'keytool -exportcert' command.
2016-10-09, 22876👍, 2💬

💬 2015-09-23 Rohan: Very helpful. 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'.
2016-09-26, 185👍, 1💬

💬 2016-09-26 eva: soooooooo Amazing thank so much this site helping to learn about blowfish algorthm more

Blowfish Cipher Algorithm
This section describes the Blowfish cipher algorithm - A 16-round Feistel cipher with block size of 64 bits developed by Bruce Schneier in 1993.
2016-08-03, 409👍, 2💬

💬 2016-08-03 azi: fantastic

"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.
2016-06-27, 10041👍, 2💬

💬 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 ...

What Is PKCS5Padding?
This section describes what is PKCS5Padding - a schema to pad cleartext to be multiples of 8-byte blocks.
2016-06-16, 11727👍, 8💬

💬 2016-06-16 yo: hola pescado

💬 2016-04-04 ankit: this is me.

💬 2016-01-28 John: Herong, thanks a lot.

💬 2016-01-27 Herong: John, the schema of PKCS7Padding can be described as below: Pad the input at the trailing end with k−(l mod k) octets with the s...

💬 2016-01-24 John: For PKCS7Padding, what is the schema? I'm interested to what is after 0x0909090909090909099

(More comments ...)

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.
2016-05-20, 113👍, 1💬

MD5 Mesasge Digest Algorithm
This chapter provides tutorial notes and example codes on the MD5 message digest algorithm. Topics include MD5 algorithm overview; using MD5 in Java, PHP, and Perl.
2016-05-19, 458👍, 1💬

💬 2016-05-19 ishvar: hello ahemad

What Is a Digital Signature?
This section describes what is a digital signature and what is the process of generating and verifying digital signature from a message.
2016-04-26, 1749👍, 1💬

💬 2016-04-26 santosh patil: Its easy to understand

"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.
2016-04-12, 2758👍, 1💬

💬 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...

Certificate X.509 Standard and DER/PEM Formats
This chapter provides tutorial notes and example codes on certificate content standard and file formats. Topics include X.509 standard for certificate content; DER encoding for certificate binary file format; PEM encoding for certificate text file format; exchanging certificates in DER and PEM forma...
2016-04-10, 130👍, 1💬

Summary - Migrating "keystore" Keys to "OpenSSL"
This section describes high level steps on how to migrate a private key generated in a JKS (Java KeyStore) file to an 'OpenSSL' key file. The key step is to convert a JKS file into a PKCS#12 file with 'keytool'.
2016-04-09, 102👍, 1💬

Cryptography Basic Concepts
This chapter describes some basic concepts of cryptography: what is cryptography, what is function and what is encryption.
2016-04-07, 1425👍, 4💬

💬 2016-02-03 dinesh: thanks

💬 2015-12-28 Herong: Malini, RSA is good example of cryptosystem. Read Introduction of RSA Algorithm for more information.

💬 2015-12-28 malini: need cryptosystem

"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.
2016-04-01, 6974👍, 1💬

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

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.
2016-03-30, 2020👍, 2💬

💬 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 ):

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.
2016-03-22, 1735👍, 4💬

💬 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

Key Schedule (Sub-Keys Generation) Algorithm
This section describes the Blowfish Key Schedule (Sub-Keys Generation) algorithm. It uses the binary representation of the fractional portion of constant Pi - 3.1415927... as initial values.
2016-03-17, 734👍, 2💬

💬 2016-03-17 Herong: Hi Yogita, Blowfish(T) function refers the Blowfish algorithm described in the previous tutorial: Blowfish Cipher Algorithm.

💬 2016-03-16 YOGITA: what is the function blowfish(T) here? Send the pseudo code

Viewing Components of RSA Keys
This section provides a tutorial example on how to view different components of a pair of RSA private key and public key using the OpenSSL command line tool.
2016-03-14, 1067👍, 2💬

💬 2015-10-02 Herong: Looks like someone is testing Base64 encoding here :-)

💬 2015-10-01 1: CSENry/M1h2AhxGSxQluy4b1ynzBGWeO320C AwEAAQJAbQQn... IQCoo0AdFXm789FfHuB+mVIKNtBLTAQNaMuX z6lXl7Ib7Q==

Viewing Components of Certificate Signing Request
This section provides a tutorial example on how to view different components of a CSR (Certificate Signing Request) for your public key with OpenSSL.
2016-03-14, 420👍, 3💬

💬 2014-03-29 Herong: Hi Mike, Sorry for the inconvenience. HTML tags are supported, but they are limited to admin users only to reduce spamming and h...

💬 2014-03-23 Mike: Wow. What a waste of time trying to make a legible comment post. No instructions on how to get a paragraph break, include a angl...

💬 2014-03-23 Mike: You made a note in "Viewing Components of Certificate Signing Request" where you said, "The request is signed with my private ke...

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.
2016-03-12, 132👍, 1💬

Key Pair Sample Program - JcaKeyPair.java
This section provides a tutorial example on how to write simple program to generate a pair of private key and public key for the RSA or DSA algorithm.
2016-03-01, 549👍, 1💬

💬 2016-03-01 Shruti: thanks

Illustration of RSA Algorithm: p,q=7,19
This section provides a tutorial example to illustrate how RSA public key encryption algorithm works with 2 small prime numbers 7 and 19.
2016-02-29, 752👍, 3💬

💬 2015-11-01 Herong: Jun, AES algorithm is added now, see Introduction to AES (Advanced Encryption Standard).

💬 2015-10-17 Herong: Jun, thank you for pointing out the mistake. I will correct it in the next version. AES will also be included.

💬 2015-10-16 jun: thanks a lot. your book makes everything clear for me except that I have not found a char for AES. By the way, I think "Generati...

RSA Implementation using java.math.BigInteger Class
This chapter provides tutorial notes and example codes on RSA implementation using Java BigInteger class. Topics include introduction of the java.math.BigInteger class; generating large probable prime numbers; generating RSA public key and private key; validating RSA keys; determining cleartext and ...
2016-02-29, 1917👍, 3💬

💬 2016-02-29 Herong: sah, is that an encoded comment?

💬 2016-02-28 sah: 7C4A8D09CA3762AF61E59520943DC26494F8 941B

💬 2014-02-06 Chinmayee: Searching for a book on RSAKey generation and got your link. Have not gone through the pdf yet. If find it good, will go for the...

Java Implementation of DES - Test Cases
This section provides two test cases for the Java implementation of DES algorithm, CipherDES.java.
2016-01-27, 131👍, 1💬

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