DSA Key generation, Sign file, Verify Signature
Key Size
Generate DSA Keys 512 bit 1024 bit 2048 bit
DSA Signer/Verifier Sign File Verify Signature Message
DSA Public Key DSA Private Key DSA

The DSA Algorithm

DSA stands for "Digital Signature Algorithm" - and is specifically designed to produce digital signatures, not perform encryption.

The requirement for public/private keys in this system is for a slightly different purpose - whereas in RSA, a key is needed so anyone can encrypt, in DSA a key is needed so anyone can verify. In RSA, the private key allows decryption; in DSA, the private key allows signature creation.

DSA Private Key is used for generating Signature file

DSA public Key is used for Verifying the Signature.

Input file to be Signed (Signature file will get downloaded)
Upload Signature file

Any private key value that you enter or we generate is not stored on this site . Also, notice that this tool is provided via an HTTPS URL to ensure that private keys cannot be stolen

OpenSSL Commands for Generatoing DSA Param, Singing File & verify File

openssl dsaparam 2048 < /dev/random > dsa_param.pem
openssl gendsa dsa_param.pem -out dsa_priv.pem
openssl dsa -in dsa_priv.pem -pubout -out dsa_pub.pem

# DSA system now made up of: dsa_param.pem, dsa_pub.pem, dsa_priv.pem

echo "foobar" > foo.txt
openssl sha1 < foo.txt > foo.txt.sha1
openssl dgst -dss1 -sign dsa_priv.pem foo.txt.sha1 > foo.txt.sig
openssl dgst -dss1 -verify dsa_pub.pem -signature foo.txt.sig foo.txt.sha1

DSA (Digital Signature Algorithm)
DSA is a variant on the ElGamal and Schnorr algorithms creates a 320 bit signature, but with 512-1024 bit security security again rests on difficulty of computing discrete logarithms has been quite widely accepted

DSA Key Generation
firstly shared global public key values (p,q,g) are chosen:
choose a large prime p = 2 power L
where L= 512 to 1024 bits and is a multiple of 64
choose q, a 160 bit prime factor of p-1
choose g = h power (p-1)/q
for any h1
then each user chooses a private key and computes their public key:
choose x compute y = g power x(mod p)

DSA key generation is related to, but somewhat more complex than El Gamal. Mostly because of the use of the secondary 160-bit modulus q used to help speed up calculations and reduce the size of the resulting signature.

DSA Signature Creation and Verification

to sign a message M
generate random signature key k, k compute
r = (g power k(mod p))(mod q)
s = k-1.SHA(M)+ x.r (mod q)
send signature (r,s) with message

to verify a signature, compute:
w = s-1(mod q)
u1= (SHA(M).w)(mod q)
u2= r.w(mod q)
v = (g power u1.y power u2(mod p))(mod q)
if v=r then the signature is verified