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Algorithms and protocols for creating signatures to documents, and verifying such signatures. These are normally asymmetric, for symmetric signatures see [mac].

1 vote
Accepted

PKCS#7 signed data structure in signed PDF document

The RFC calls this "external signature"; IME it is also called "detached signature" or "clear-sign[ing,ed]", and is widely used. … to be handled by a non-SMIME-aware or even non-MIME-aware program (only without signature verification). …
dave_thompson_085's user avatar
4 votes

How do you communicate the hash function used with RSA signing?

As @Myria describes one common RSA signature scheme, defined in the original PKCS#1 as type 1 and retronymed RSASSA-PKCS1-v1_5 in the nearly current version encodes the hash inside the value computed modexp … Important examples: SSL and TLS through 1.1 for protocol signature (ServerKeyExchange and clientCertVerify) use a fixed hash for RSA (combined MD5 and SHA1), SHA1 for DSA (as required by the versions …
dave_thompson_085's user avatar
2 votes

Does the Server Key Exchange sign a hash or text

As to the specs, note that 4.7 says In RSA signing, the opaque vector contains the signature generated using the RSASSA-PKCS1-v1_5 signature scheme defined in [PKCS1]. ... … referencing (then-current) RFC3447 which unambiguously defines the whole signature process: hash, then encode, then pad, then the RSA modular exponentiation. …
dave_thompson_085's user avatar
7 votes

How does openssl signature verification work?

It depends on the type of key, and (thus) signature. … Again the signature is mathematically a pair of integers, represented in ASN.1. …
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6 votes
Accepted

PKCS#7 CMS - Message digest calculation process

hash is used in signature generation and verification (RSA, EG, DSA, and ECDSA). … The details of the signature generation depend on the signature algorithm employed. [...] …
dave_thompson_085's user avatar
2 votes
Accepted

Signing a GPG Public Key

In your posted message-and-decode, the signature given is a valid v1_5 signature for the SHA512 hash 89 6e e3 83 f0 24 e7 ba 4e 12 87 36 bd dd 55 fb 1d 8e 20 b0 f2 72 c6 3c e3 53 29 23 47 41 28 c9 b7 f4 … 51 ea 39 cd 1c ae ee 29 c2 e4 d4 13 fb 05 dd 89 bd 6b f7 20 76 63 95 f5 f8 b7 79 b2 d1 1b -- or to be exact, since the v1_5 signature scheme includes hashing, it is the signature for data with that SHA512 …
dave_thompson_085's user avatar
1 vote

Unable to reproduce correct signature data

Most other public-key signature schemes, and essentially all public-key encryption schemes (and symmetric encryption schemes also), when executed multiple times on the same data (and key) produce results …
dave_thompson_085's user avatar
5 votes
Accepted

Why is data signed with SHA256-RSA-PKCS and digest signed with RSA-PKCS different?

Except for being PKCS11 (hardware) rather than software, this is crossdupe at least: https://stackoverflow.com/questions/521101/using-sha1-and-rsa-with-java-security-signature-vs-messagedigest-and-cipher … https://stackoverflow.com/questions/62955968/how-can-realize-openssl-pkeyutl-sign-by-java https://stackoverflow.com/questions/48013643/get-the-sha1-hashed-value-from-xml-signature-value https://stackoverflow.com …
dave_thompson_085's user avatar
4 votes

How does Diffie Hellman protocol work in Bitcoin Blockchain Transactions?

Bitcoin does not use ECDH, or any DH, at all. It does use ECDSA (on secp256k1). The formula you posted is a wrongly-cased rearrangement of part of DSA, which with notational change is also used for EC …
dave_thompson_085's user avatar
6 votes
Accepted

DSS security in comparison to ECDSA or RSA

As noted in comments, DSS strictly means the Digital Signature Standard, a document (FIPS 186) published by NIST, a part of the US government. … The original version of FIPS 186 in 1994 defined (and was the original definition of) a single algorithm, DSA the Digital Signature Algorithm. …
dave_thompson_085's user avatar
3 votes
Accepted

ECDSA-SHA256 HTTP Signature String Construction

See Shouldn't a signature using ECDSA be exactly 96 bytes, not 102 or 103? … /java-ecdsawithsha256-signature-with-inconsistent-length and more dupes you can find by following 'Linked' …
dave_thompson_085's user avatar
3 votes

Is signature same as hash value encrypted with the private key in openssl?

See PKCS1 now at RFC8017; encryption and signature are different things -- and for all PKC not just RSA, publickey encrypts or verifies, privatekey decrypts or signs (see wikipedia). openssl pkeyutl -encrypt … See also my long list of Qs explaining that signature is not encryption Also, encryption is randomized; if you encrypt twice you get different results, so you couldn't determine correctness just by comparing …
dave_thompson_085's user avatar
6 votes

setting the MGF hash to a different value other than the regular hash with openssl for PSS s...

Meta: since this is about using a tool not the underlying algorithm/math AIUI should be security.SE instead. If anyone can and wants to migrate feel free. Per 1.0.2 source, -sigopt rsa_mgf1_md:name w …
dave_thompson_085's user avatar
2 votes
Accepted

PKCS#7 SignedData - how is the "encryptedDigest" constructed for RSAES‐PKCS‐v1_5?

(Since signature depends on having exactly the same bits, and the whole point of DER is to produce the same bits suitable for signature, it's not at all clear why v1 only specified BER for data so small … For the DigestInfo in PKCS1 RSA signature rfc3447 et seq shows them as explicitly NULL and that's what everybody does. …
dave_thompson_085's user avatar
2 votes

Regarding the Digital Signature Algorithm During Client Authentication in TLS 1.2

In TLS 1.2, the sigalgs extension in ClientHello lists signature schemes the server is allowed to use; a similar but separate field in CertRequest lists thost the client may use, and the actual (chosen … And yes-ish, the signatureAlgorithm field in a certificate describes the signature on the body of the certificate by the issuing (parent) CA, but that is usually an intermediate CA not the root CA; it …
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