Status at a glance:

Scalar Crypto Specification:

Lightweight instruction set extensions for RV32 and RV64 HARTs.  Proposed extensions:

  • Extensions fully defined in the Scalar Crypto Specification:  Zk, Zkn, Zks, Zkr, Zkne, Zknd, Zknh, Zksed, Zksh, Zkt
  • Shared with the Bit-Manipulation Specification: Zbkx, Zbkc, Zbkb
  • Instruction Group Names Diagram (click thumbnail for full-size image)


Architecture & Opcode consistency review

  • The results of the review can be seen here. Scalar Crypto Arch Review Results.pdf
  • After discussion within the task group, the following changes will be made to the spec, with the changes expected to land in 0.9.4 before the end of August.
    • Stop overlapping the aes32 and aes64 opcodes. See riscv/riscv-opcodes#77
    • Clarify the effect of misa.k
    • Some updates to the entropy source and zkt detailed here.
    • Miscellaneous editorial issues.
  • Some downstream tasks for our group development partners now we are in public review.
PLCTGCCNot startedUpdate extension names: Zkb → Zbkb etc.
PLCTGCCNot startedUpdate aes32/64* encodings if applicable.
PLCTLLVMDoneUpdate extension names: Zkb → Zbkb etc.
PLCTLLVMDoneUpdate aes32/64* encodings if applicable.
IITriscv-configNot startedUpdate extension names: Zkb → Zbkb etc.
IITriscv-configNot startedUpdate instruction inclusion in different extensions
IITriscv-arch-testsNot startedBreak up K suite into Zk* extensions
IITriscv-arch-testsNot startedUpdate instruction inclusion in different extensions

Architecture Tests

  • Test plan for the scalar-crypto specific instructions is available.
  • Imperas have a complete set of tests, written to the existing test plan, for the scalar crypto instructions and the bitmanip instructions we borrow.
    • These have been merged into the main test suite as of PR#177, with many thanks to Imperas for the contribution.
      • Spike, OVPSim and Sail all agree on the test signatures.
    • They form a base we can use to develop prototype implementations / Spike / SAIL / QEMU very easily and quickly.
  • Upstream Spike support for enabling it to work with the K test suite is being added in PR#687.
  • IIT Madras are also looking at writing the scalar crypto tests for integration into the official architectural tests repo as well.
    • Agreed SoW for IITM
    • They are re-implementing the tests as part of the blessed coverage and test generation tooling.
      • Making good progress with the simple test patterns for scalar-crypto specific instructions A/O April 7'th '21
    • We then switch over to using the IIT tests when they are finished, since they will be easier to maintain/extend going forward than the Imperas tests.
  • YAML config changes for K have been merged in. See here.
  • Update from IIT Madras as on 25-Oct
  • Status from IIT Madras as on 17-Jun:
    • All test cases and coverage reports has been generated and presented.
    • If there are any changes in future on these that is required in future, IIT Madras will enhance the scripts as per requirements.
  • Status from IIT Madras as on 20-May:
    • Real world test cases as per the test plan has been generated.
    • Currently waiting for the fixed toolchain with K extension from PLCT to test the generated test cases. All the test cases are working fine when we run against the patched toolchain
    • A PR has been raised with a pull request for this suite to be reviewed and merged in the riscv-arch tests github repo.
  • Status from IIT Madras as on 12-May:
    • Coverage report for all developed cases in CTG/ISAC has been generated and it is reported as 100%
    • Currently real world test cases are being developed as per test plan and will be completed and send for review by beginning of next week
  • Status from IIT Madras as on 05-May:
    • Resolved issues in running the rv64ik toolchain after interacting with PLCT and compile the relevant tests generated from CTG and run them on spike
    • Currently resolving issues in the running the rv64ibk toolchain. Once this is done, will generate the coverage report of the test cases built till now and share with team.
  • Status from IIT Madras as on 26-Apr:
    • Completed the coverage points specification for all 32-bit and 64-bit instructions
    • Generated test cases from the coverage points
    • Currently working on trying to install the scalar crypto enabled toolchain.

Compilers / Toolchains

Imperas maintain pre-built toolchains for various in-progress RISC-V extensions here. See the "rvk-*" branches for scalar crypto.

GCC and Binutils


  • Work will be done by PLCT lab under the group contributor model.
  • Slides from PLCT Update Weds 10'th Feb
  • As of 21'st April '21, LLVM work is mostly complete, waiting on PLCT lab for an update about merging things upstream.
    • Some small changes will be needed as we move to v1.0 of scalar crypto around encodings.
  • As of 24'st Jan '22, LLVM upstream is able to compile the assembly code of Zk* and Zbk*


Though all listed under "simulators", these are actually a collection of formal model / virtual machine / architectural simulators / DV simulators etc.


  • Currently working on getting support merged in upstream in PR#99
    • Support for all scalar-crypto dedicated instructions and the entropy source is present.
    • No support for Bitmanip yet.


  • Upstream support has been merged in.
  • Instructions are up to date with v1.0.0


  • Imperas Commercial Simulator
  • Freeware version
  • Supports:
    • Crypto-scalar v0.7.2, v0.8.1, 0.9.0,  0.9.2, 1.0.0-rc1, + Bitmanip subsets
    • Bitmanip 0.90, 0.91, 0.92, 0.93-draft, 0.93, 0.94, 1.0.0
    • Functional coverage collection.


Proof-of-Concept implementations


Project NameBase ArchitectureLevel of implementationNotes
Stand-alone functional unitsRV32/64Yosys SynthesisStand-alone functional-unit style implementations of the dedicated scalar crypto instructions. Free to use as "drop-ins" for prototyping.
scarv-cpuRV32Behavioural RTL simulation / Yosys Synthesis / FPGA

Completely Public/Open Source. Useful as a public baseline. Commercial implementations should aim to be better than this!

PQShield security coreRV32(assumed) Behavioural RTL simulation. Running on FPGA.Closed / commercial source - PQShield.
Minidice TRNGN/AFPGA ImplementationClosed / commercial source - PQShield. Complete implementation of the RISC-V entropy source.
Romain Dolbeau / VexRISC-VRV32Running on FPGA.Uses VexRiscv core as a base. Completely independent implementation from scratch, outside the Crypto TG.
IQonIC Works RV32IC_P5RV32In development"implemented Zkn (...), along with selectable Zb* and Zkb. We also have an optional custom extension that does AES block encrypt/decrypt, and a bus-based AES/cipher-mode accelerator. Work in progress benchmarking them on FPGA to compare relative performance in accelerating crypto library functions."
croyde-riscvRV64Behavioural RTL simulation / Yosys Synthesis / FPGA3-stage RV64 micro-controller. rv64imck. Free/Open source. Something commercial implementations should better. Implements everything except ZKR.
  • (warning) We still need RV64 implementations. (warning)
  • Barry Spinney has offered to do advanced node synthesis runs for open source implementations.
    • I (Ben) intend to take him up on this when I get time. No idea when that will be.


Romain DolbeauIndependent implementations of various important ciphers + modes of operation.
rvkrypto-fips / Markku"FIPS 140-3 and higher-level algorithm Tests for RISC-V Crypto Extension"
riscv-crypto benchmarksInitial benchmarks used to develop the scalar crypto extension.

ABI Extensions

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