JCE Utility and Extension Packages
org.bouncycastle.jce: Utility classes for use with the JCE.
org.bouncycastle.jce.examples: Example classes for use with the JCE.
org.bouncycastle.jce.exception
org.bouncycastle.jce.interfaces: Interfaces for supporting Elliptic Curve Keys, El Gamal, and PKCS12 attributes.
org.bouncycastle.jce.netscape
org.bouncycastle.jce.spec: Parameter specifications for supporting El Gamal, and Elliptic Curve.

OCSP and OpenSSL PEM Support Packages
org.bouncycastle.ocsp: Classes for dealing Online Certificate Status Protocol (OCSP) - RFC 2560.
org.bouncycastle.ocsp.test: Test class for OCSP messages.
org.bouncycastle.openssl: Classes for dealing with OpenSSL PEM files.
org.bouncycastle.openssl.test: Test class for OpenSSL PEMReader.

ASN.1 Support Packages
org.bouncycastle.asn1: A library for parsing and writing ASN.1 objects.
org.bouncycastle.asn1.bc
org.bouncycastle.asn1.cmp: Support classes useful for encoding and supporting PKIX-CMP as described RFC 2510.
org.bouncycastle.asn1.cms: Support classes useful for encoding and supporting Cryptographic Message Syntax as described in PKCS#7 and RFC 3369 (formerly RFC 2630).
org.bouncycastle.asn1.cms.ecc
org.bouncycastle.asn1.crmf
org.bouncycastle.asn1.cryptopro: Support classes for CRYPTO-PRO related objects - such as GOST identifiers.
org.bouncycastle.asn1.eac
org.bouncycastle.asn1.esf: Support classes useful for encoding and supporting [ESF] RFC3126 Electronic Signature Formats for long term electronic signatures.
org.bouncycastle.asn1.ess: Support classes useful for encoding and supporting Enhanced Security Services for S/MIME as described RFC 2634 and RFC 5035.
org.bouncycastle.asn1.gnu
org.bouncycastle.asn1.iana
org.bouncycastle.asn1.icao: ICAO ASN.1 classes for electronic passport.
org.bouncycastle.asn1.isismtt
org.bouncycastle.asn1.isismtt.ocsp
org.bouncycastle.asn1.isismtt.x509
org.bouncycastle.asn1.kisa
org.bouncycastle.asn1.microsoft
org.bouncycastle.asn1.misc: Miscellaneous object identifiers and objects.
org.bouncycastle.asn1.mozilla: Support classes useful for encoding objects used by mozilla.
org.bouncycastle.asn1.nist: Support classes for NIST related objects.
org.bouncycastle.asn1.ntt
org.bouncycastle.asn1.ocsp: Support classes useful for encoding and supporting OCSP objects.
org.bouncycastle.asn1.oiw: Objects and OID for the support of ISO OIW.
org.bouncycastle.asn1.pkcs: Support classes useful for encoding and supporting the various RSA PKCS documents.
org.bouncycastle.asn1.sec: Classes for support of the SEC standard for Elliptic Curve.
org.bouncycastle.asn1.smime: Support classes useful for encoding and supporting S/MIME.
org.bouncycastle.asn1.teletrust: Support classes for TeleTrust related objects.
org.bouncycastle.asn1.tsp: Support classes useful for encoding and supporting Time Stamp Protocol as described RFC 3161.
org.bouncycastle.asn1.util: An ASN.1 dump utility.
org.bouncycastle.asn1.x500
org.bouncycastle.asn1.x509: Support classes useful for encoding and processing X.509 certificates.
org.bouncycastle.asn1.x509.qualified: Support classes useful for encoding and processing messages based around RFC3739
org.bouncycastle.asn1.x509.sigi
org.bouncycastle.asn1.x9: Support classes useful for encoding and supporting X9.62 elliptic curve.

Lightweight Crypto Packages
org.bouncycastle.crypto: Base classes for the lightweight API.
org.bouncycastle.crypto.agreement: Basic key agreement classes.
org.bouncycastle.crypto.agreement.kdf
org.bouncycastle.crypto.agreement.srp
org.bouncycastle.crypto.digests: Message digest classes.
org.bouncycastle.crypto.encodings: Block encodings for asymmetric ciphers.
org.bouncycastle.crypto.engines: Basic cipher classes.
org.bouncycastle.crypto.examples: Simple examples of light weight API usage.
org.bouncycastle.crypto.generators: Generators for keys, key pairs and password based encryption algorithms.
org.bouncycastle.crypto.io: Classes for doing "enhanced" I/O with Digests and MACs.
org.bouncycastle.crypto.macs: Classes for creating MACs and HMACs.
org.bouncycastle.crypto.modes: Modes for symmetric ciphers.
org.bouncycastle.crypto.modes.gcm
org.bouncycastle.crypto.paddings: Paddings for symmetric ciphers.
org.bouncycastle.crypto.params: Classes for parameter objects for ciphers and generators.
org.bouncycastle.crypto.prng: Lightweight psuedo-random number generators.
org.bouncycastle.crypto.signers: Basic signers.
org.bouncycastle.crypto.tls: A lightweight TLS API.
org.bouncycastle.crypto.util: Some general utility/conversion classes.

Utility Packages
org.bouncycastle.util
org.bouncycastle.util.encoders: Classes for producing and reading Base64 and Hex strings.
org.bouncycastle.util.io
org.bouncycastle.util.test: Light weight test API.

JCE Provider and Test Classes
org.bouncycastle.jce.provider
org.bouncycastle.jce.provider.asymmetric
org.bouncycastle.jce.provider.asymmetric.ec
org.bouncycastle.jce.provider.symmetric
org.bouncycastle.jce.provider.test
org.bouncycastle.jce.provider.test.nist
org.bouncycastle.jce.provider.test.rsa3
org.bouncycastle.jce.provider.util

Other Packages
org.bouncycastle.mozilla: Support class for mozilla signed public key and challenge.
org.bouncycastle.x509: Classes for supporting the generation of X.509 certificates and X.509 attribute certificates.
org.bouncycastle.x509.examples: Examples for X.509 attribute certificates.
org.bouncycastle.x509.extension: Helper classes for dealing with common X.509 extensions.
org.bouncycastle.x509.util