OpenSSL

OpenSSL is a robust, commercial-grade, full-featured Open Source Toolkit for the Transport Layer Security (TLS) protocol

Featherduster

For breaking crypto; It tries to make the process of identifying and exploiting weak cryptosystems as easy as possible

CrackStation

Crack known hashes LM, NTLM, md2, md4, md5, md5(md5_hex), md5-half, sha1, sha224, sha256, sha384, sha512, ripeMD160, whirlpool, MySQL 4.1+

Hashes.com

Decrypt MD5, SHA1, MySQL, NTLM, SHA256, SHA512 hashes

Hash_extender

Hash length extension attack

PkCrack

Breaking PkZip-encryption ciphers

RsaCtfTool

RSA multi attacks tool : uncipher data from weak public key and try to recover private key

Rsatool

Calculates RSA (p, q, n, d, e) and RSA-CRT (dP, dQ, qInv) parameters given either two primes (p, q) or modulus and private exponent (n, d)

Xortool

XOR analysis, guess the key length or key

John

Enhanced, "jumbo" version of John the Ripper supports hundreds of hash and cipher types

Ophcrack

Free Windows password cracker based on rainbow tables

Quipqiup

An online tool for breaking substitution ciphers or vigenere ciphers (without key)

Vigenere

online tool breaks Vigenere ciphers without knowing the key

One Time Pad

Online tool for playing with one-time pad ciphers

Unshadow

Tool combines the passwd and shadow files so John can use them

Onlinehashcrack

Cloud Password Recovery Services assisting cyber security experts. WPA / Office / iTunes / Archive / PDF / Password / Hashes

Cmd5

Yet another site to decrypt hashes they also claim to brute force it within 5 days if it's not in their DB?

Truecrack

TrueCrack is a brute-force password cracker for TrueCrypt (Copyrigth) volumes (GPU support)

Ciphey

Automatically decrypt encryptions without knowing the key or cipher, decode encodings, and crack hashes

Cryptii

Web app offering modular conversion, encoding and encryption online. Translations are done in the browser without any server interaction. Very handy CTF tool!

CyberChef

The best online tool for analysing and decoding data

Etherblob-explorer

Search and extract blob files on the Ethereum Blockchain network

Go-ethereum

Official Go implementation of the Ethereum protocol. Quick way to download block data via geth.

ETH-block-by-date

Get Ethereum block number by a given date. Or blocks by a given period duration. Works well with Web3 node js.

Web3.js

Ethereum JavaScript API.

Web3.py

A python interface for interacting with the Ethereum blockchain and ecosystem. Based on Web3.js