I'm familiar with basic cryptography in java But have zero experience in bouncycastle, Recently I came across a requirement that needs to read an encrypted and signed file from FTP.

The sender has directed me to use bcfips ebook for reading those encrypted and signed files. I went through the download page of the bouncy castle website, But I'm confused by a lot of jargon that I can't understand and I don't know which jar file should I use.

I'm wondering what's the difference between bcprov and bcpkix and bcfips?

I appreciate it if someone points me on the correct path.

CodePudding user response：

bcprov contains the Java provider as well as the "lightweight API". Bouncy Castle has got a lot of functionality and their own specific architecture and API. The Java provider provides this functionality as services to Java, so that the algorithms can be used from generic classes such as Cipher. It also contains a lot of utility classes, some of which are required for the provider. Everything is available to the user, which means that it is a bit of a maze and there is a higher chance that updates break software (e.g. there have been a few updates of the ASN.1 encoder / decoder that weren't backwards compatible.

The reason to use this library is the extended functionality that is provided. However, you should keep in mind that the default Java providers can be software / hardware optimized and may be more secure/better tested as well. So before choosing it you should definitely check if the algorithms are not present in the Java provided algorithms.

bcfips is the certified FIPS provider. FIPS uses a specific set of algorithms defined by NIST and bcfips therefore contains a subset of the functionality provided by bcprov. FIPS also has strict rules when it comes to e.g. destruction of key material. FIPS certification is rather expensive and time consuming and BC would want you to get a support contract when using their FIPS provider.

You may need this library if your software is required to use FIPS certified algorithm implementations. Note that they will still be implemented in software and will therefore e.g. not use AES acceleration.

Now bcpkixis a different beast altogether. It provides support for "PKIX/CMS/EAC/PKCS/OCSP/TSP/OPENSSL" protocols and container formats.

The following modules are present:

• PKIX (in the cert package) means "X.509 based Public Key Infrastructure and contains support for certificates, certificate requests, CRL's etc.; the same type of certificates that are used for TLS that is used for HTTPS, i.e. the secure connections that your browser uses. There are some separate related packages inside the main package:
  • cmc: Certificate Management over CMS
  • dvcs: Data Validation and Certification Server Protocols
  • est: Enrollment over Secure Transport
• CMS means Cryptographic Message Syntax, a format to envelope (i.e. encrypt) and sign messages in a structural way. CMS is a flexible, descriptive format, i.e. it indicates which algorithms are used and helps with key management. It uses X.509 certificates and is based on the same technology.
  • MIME: related to CMS, SMIME is the use of CMS within the email protocols.
• EAC is a technology used for European ePassports. It stands for Extended Access Control, which can be used to gain access to e.g. the fingerprint or - in the case of the German passport - additional personal information, assuming you've got the right set of certificates and keys of course.
• PKCS stands for Public Key Cryptographic Standards, historically created by "RSA Laboratories", however the classes mainly seem to support PKCS#8 (private key storage), 10 (certification requests) and 12 (key / trust stores).
• OCSP is the Online Certificate Status Protocol, used to check the status of X.509 certificates, e.g. when using TLS.
• TSP means Time Stamping Protocol, a method of signing messages together with a date / time from a trusted source (it can also mean Trusted Service Provider, but here it doesn't).
• OpenSSL is of course a library and application. It has some specific / proprietary methods concerning key derivation from passwords and the application of these in PKCS#8 encrypted private keys.

The operator in the PKIX library seems to be a way to operate directly on the "lightweight API" or on the JCA provided API using a generalized interface (basically a way of performing dependency injection).

You'd use this library if you need to implement any of the higher level protocols / container formats. Many of these formats are relatively old, so you might be looking for e.g. NaCL or similar software for more up-to-date protocols and container formats. That said, CMS certainly can be secured and having these protocols implemented is great for (backwards) compatibility with existing systems.

This answer took a bit of writing. If I'm not mistaken the PKIX library can be used without installing the Bouncy Castle ("BC") provider, except when you're using specific algorithms not present in your Java runtime. However, the documentation of Bouncy Castle is very sparse, most packages do not even explain what they are for or how they can be used.